One word. Points!
And a little pay back to those that rate me as well. My current scheme is this. If you fan me, rate me an 11 or 10 or rate one of my photos an 11 I:
Rate your profile a 10 (all I can)
Become a fan of you
Rate all the pics in your default folder (bandwidth allowing)
On occasion I do this to random people I see go by with an interesting profile pic.
Either way I get pretty good odds on those people coming back and rating more and fanning me. Lots of points for everybody.
I used to only fan people I thought had interesting pics but started the above to improve the point flow. Now it is confusing as to which fans have the good pics so I'll drop them a friend request too. That reminds me I probably need to go through my fan list and drop a few friend requests.
Basically if you not in my family then I really do not know much about you. But then as I see it this site is really all about the points. If you actually think I'm someone you would like to talk to drop me an email. As you can probably see from the above it is easy it get lost in the flood by being subtle. ;-)