I don't want to criticize other people's uses of the internet, but sometimes my philosophy runs counter to the intuition of many. On flickr, there is a sizable portion of the community that is interested in what can best be described as amateur porn. This is entirely understandable, as sex is popular (whether you like it or not), and I respect flickr for allowing it, because otherwise, I would likely not be permitted to make 'artistic erotica' that borders the line of the explicit, and would therefore either have to give up my passion for erotic photography, or else find some other place to showcase my work.
Most of the people who are into this amateur porn sharing activity are less like me - with a driving artistic passion - and more of the 'let the horny pics flow' variety. Moreover, though they are undoubtedly sexually liberated, I get the sense that in most cases their sexual liberation is a 'secret' from their public and professional lives, whereas I - though I don't advertise my sexual interests to my friends (well, maybe a little) and family (to say nothing of business associates), neither am I committed to keeping it a big secret, because I respect honesty and transparency, and I think that sex should be less stigmatized and the only way to do that is to fight back against the 'deny it and pretend it doesn't happen' mentality.
Not everyone, though, is in a position to be able to afford the potential blow to their reputation should others find out about their proclivity for sexy "mis"deeds. And so, there is some concern about privacy when sharing pics online. Now, I agree that general concerns about privacy on the internet are valid and important, as regards personal information. But when the point of an activity is to share pictures, it seems counterintuitive to go to lengths to control the distribution of those pictures in certain ways. Most people keep their pictures on flickr private so that only specific people they add to their designated contact list can then see the pictures they share. This serves the purpose of preventing anyone not interested in seeing those pictures from seeing them, and only allowing those to see them who have expressed an interest in seeing them (and in some cases, having something in return).
On the first concern, I can't help thinking that flickr's safety filters already do the job of preventing people who don't like porn from seeing it. Of course, somebody who likes to see porn (or doesn't, but is willing to look for investigative purposes) will be able to see it even if you don't want them, specifically, to see it (say, a friend of yours or a family member who you'd rather not know you were into this sort of thing). On the other hand, people put up these "walls" of privacy that are mostly illusory, that do more to lull you into a false sense of security than to really prevent information from getting into the wrong hands. Any person you let past your wall of defense can take your pictures and then post them anywhere else, without your permission. Most of the people coming in are largely anonymous anyway (because they, like you, don't want their activities to be known), so you can't possibly know them well enough to trust them, and limiting access to only the most trusted has the effect of 1) pretty much defeating the purpose of sharing in the first place, and 2) not keeping you 100% safe anyway, because people you trusted can turn on you, or prove to be less trustworthy than you thought, or even cause problems unintentionally by making mistakes.
So, I say, if you're posting pictures on the internet, chances are they could end up anywhere. Which means two things. If you absolutely cannot deal with having to defend that picture no matter who sees it, then you really should not be uploading it to the internet*, unless you're prepared to deal with the regret and fallout should you gamble on the risk of nobody important finding out, and lose. The other thing this means is that if you're posting a picture on the internet that you're capable of defending even if your, say, grandmother** ends up finding it (as unlikely as that is, it is not impossible), then there's really no reason to put up any extraneous privacy walls other than trying to keep that picture in a place where people who want to see it can find it and people who don't can easily avoid it (although this is only an issue of social politeness).
* Of course, sending private pictures to your boyfriend/girlfriend/someone you trust by email is an entirely different matter than posting pictures on a photo sharing sight to be viewed and admired by anonymous strangers.
** Ex: Say I have a relative who is conservative and very religious. I'd rather not have her know that I pose for sexually explicit pictures and share them with strangers on the internet. On the other hand, if she found out, I'm not going to deny it, and I'm not going to hang my head in shame either. This is a part of who I am, and while it's unfortunate if she doesn't like it and chooses to judge me for it (the possibility of which is the reason I don't go out of my way to tell her), I'm not going to change, and I'm not going to feel sorry for myself because someone else doesn't like what I do.
And that's how I do things. I did mention another concern, which is the 'barter' system of internet trading - "you can't see my pictures unless you have some pictures of your own to show me." I think it's great to encourage people to go out and take more pictures for us all to see, but I'm not going to require that someone have a picture of interest to me before I allow them to take pleasure in viewing what pictures I have. Some groups on flickr also have this policy, in that you will not be allowed to join unless you have pictures to contribute that fit the theme of the group. While it's great to have contributing members, it seems kind of discriminatory for me not to be able to join a group to advertise my appreciation for erotic nudes of women, just because I haven't really had the chance to take any erotic pictures of women myself. Do you see what I mean?
Anyway, there's definitely a poor opinion of "leechers" and "lurkers" in internet communities, and while in some cases that opinion is warranted, in others it looks to me like your typical discrimination against voyeurs and people who lack opportunity and those who are more passive and like to observe the world more than interact with it. That's not to say that they're worthless and don't have anything to contribute, just that they go about it in a different way, and you really shouldn't discriminate against them just because they behave differently than what you're used to.
In short, to paraphrase what I've said before, I'm not about hazing and private communities and secret privileges. I'm about honesty and transparency and giving power to the people.