I love the input everyone is contributing. Seeing lots of cool ideas and things to consider.
I'd have no problem not requiring reciprocal links. Hell, I have two lists right now that don't require recips. (
http://www.whoringwives.com and
http://www.filthyearl.com ) Content should always be the focus. As several of you have stated, you want/need to build a site that gains links naturally, not forcefully. You have to create the type of pages that people find and want to share. That's where the magic is.
I love pc's idea of using FB applications in order to handle login and commenting. That's a lot easier than scripting your own system that will work across different areas of a site. Plus, most people are probably already logged in to FB while surfing, so they could comment on something without needing to sign up to your own site. And allowing people the ability to comment on pages gives them the feelings of community and ownership. That's a site they'll come back to.
Now, the problem is, what is it that this hybrid monster would publish? Blog posts with embedded images and streaming videos? Galleries? Etcetera? Plus, if you want your "members" to feel like they're part of the site, what can they contribute other than pics of their girlfriends? Chances are, they're going to be post images they took from someone else's site.
Keep the input and feedback coming. By the way, I have no actual intention of creating a project like this in the immediate future. I might tweak PerveSpace a bit to add some of these functions, but I'm not launching anything huge anytime soon.