Disclaimer: I make no claim that the advice given in this post is accurate. Standards change, and not every guideline is always clear to follow. These are simply the rules as I understand them at the time of writing this post. That understanding may change, and the rules themselves may change. I make no guarantee that by following these guidelines you will avoid running into trouble with flickr, or other flickr users. To stay safe, please visit the flickr community group Adult Flickr Members: How NOT to get Deleted!, and read their posts and guides thoroughly and frequently. ;-) Good luck.
Safety filters are the ingenious invention that allows flickr to play host to both family friendly content, as well as hardcore pornography. But, they are of course not perfect. They are essentially an imperfect solution to the problem of how to serve a global community where members from different parts of the world are bound to have different standards of decency.
There are only three levels of safety. "Safe" is basically anything that is completely inoffensive, whereas "restricted" is reserved for the really bad stuff, and "moderate" is for those things that tend to fall in between. Of course, illegal material of any kind is outright prohibited.
The biggest complaint I have about the safety filters (and it's something I can live with, even though I don't like it), is that nudity is not judged independently of sexual content. I understand that it's a lot harder to judge the context of an image to determine whether or not it's sexual than to just take a quick look and see what parts of the body are visible, but the result of taking the easy way out is that you get nonsexual nudity placed on the same level as explicit sexual penetration. A set of genitals ten feet from the camera is no less severe, according to the safety filters, than a set of genitals ten inches from the camera, and inserted into another set of genitals...and covered in goo. Now what kind of message does that send out?
Consider how the "restricted" level is described right there in flickr's FAQ:
Restricted - This is content you probably wouldn't show to your mum, and definitely shouldn't be seen by kids
Notice the discrimination against nudists. A nudist would have no problem showing his naked body to his [nudist] mum, nor would he have any qualms about showing it to [nudist] kids. In fact, in nudist environments, mums and kids alike frequently hang out together, in the altogether - that is, completely nude. And there's nothing sinister or sexual about it.
I realize we're talking about a minority here, but I'm part of that minority, and so it has to be said. Still, I can tolerate the fact that most people are offended by nudity (even though I don't like it), but the thing that bugs me more is that it's being equated with sexuality. I know there are people out there who can stand to view nudity uncensored (whether in a nudist or artistic context, or something else), but still have hang-ups about porn. But the way the safety filters work, you can't pick one or the other, they come together as a package deal. If you want to view uncensored nudity, you have to put up with the possibility of coming across porn, and if you can't stand looking at porn, then you have to deal with looking at only nudity that has been censored (or none at all). Again, what kind of message does this send out?
Let's take a closer look at the filters, and what falls under each safety level. Thankfully, flickr has included in its FAQ their favorite 'rule of thumb' regarding posting material that includes nudity. It goes like this: breasts and bottoms are moderate, full frontal nudity is restricted. And, one of the unspoken rules is, if your content is sexualized in any way - either by comments or tags or descriptions or by placing it in certain groups or even in the context of the rest of your photostream - you should filter it one level higher than usual. For example, a picture of bare feet, while technically including only safe levels of "nudity", might need to be rated moderate, or even restricted, if it is contextualized as a 'foot fetish' photo. This is true even for fetish items that are not strictly defined as a form of 'nudity'.
But for this exercise, let's take the following photos as is, ignoring their context, so we can see what the different safety levels allow for (in my own understanding). However, I'll note that, when in doubt (and sometimes when there is no doubt), I tend to filter my photos conservatively - for two reasons. One, the cost of reducing a photo's audience (which is admittedly unfortunate) is minor compared to the potential cost of getting in trouble (and possibly even deleted) for not filtering a moderate or restricted photo properly. Two, there are some photos that might technically be able to survive on a lower safety level, but I don't necessarily want them to be seen by people surfing on just that level, for personal reasons.
So, starting with "safe", the range goes from the fully dressed, purely mundane,
to family-friendly not-really-showing-anything implied nudity.
Many flickrites get away with creating the illusion of implied nudity via skimpy clothing - and they are the ones who tend to make a big fuss about the fact that they're not really naked, thereby spoiling the fun - but I've always gone for the authentic approach; that's just my style.
In the "moderate" camp, we have breasts and bottoms. Note that there is no top-equality on flickr. Shirtless men can be considered safe (if not overtly sexualized), but topless women cannot. That's just the way it is. Breasts and bottoms are officially "nudity", yet relatively harmless in comparison to full-on genitalia - think breastfeeding and mooning - so they come in at "moderate".
Now, I know people freak out when they see genitalia, but I can't help thinking that it's ridiculous that - for example - a nudist in the same innocent pose would be rated moderate when viewed from one direction, yet restricted when viewed from another. It just seems silly.
And so we come to "restricted", which covers everything from a flash of pubic hair,
less revealing nudity that is nevertheless sexualized,
full frontal nudity in a nonsexual context,
tastefully sexualized nudity,
all the way up to explicit hardcore pornography
(quite a range, eh?). And then you've got frustrating cases like this one, or this one, or this one, or, yes, even this one (which is certainly no more disturbing than the phallic imagery - including penis-shaped lollipops - a person might be exposed to at a public fertility festival in some parts of the world), where the "offending" bits are so small or nondescript that they are essentially benign (but better safe than sorry - er, sorry, better restricted than...uh, never mind).
As I said before, I resent the fact that immodest nudity and hardcore sexuality are judged on the same level. I don't mind there being a filter for nudity, but I think it's unfortunate that it's the same filter that is used for pornography. I have pictures that I would be comfortable showing to nudists and art lovers, yet I would not be comfortable showing them other pictures I have that could be described as pornographic. But instead of separating that content, it's all or nothing. And that goes against the very purpose of the safety filters - to let people view the content they want, while avoiding the content they don't want.
Those are my complaints, and as I said, I can live with the way the system currently works, whether I like it or not - that's the basis of free speech, being able to criticize something constructively. I do have much good to say of flickr, since they are the only service I've found so far that meets my needs of having a nice community, and explicitly allowing pornographic material, while not behaving like a sleazy 'adult industry' site. For that they have my kudos. My growth as a photographer has been greatly facilitated by the flickr service and community, and who knows how differently things would have progressed without it.
On the other hand, you hear a lot about people being deleted from flickr for breaking this or that community standard. I'd like to think that my courteous behavior and careful reading of the rules is what's responsible for me being kept around this long, rather than blind luck (and really, so many people do get deleted for really obvious reasons), but the content I post does put me sort of on the fringe, and I'm not impervious to making mistakes. But so far, pretty good. I'm crossing my fingers that it stays that way.