I have been here for about 2/3 weeks ish and only today lol i noticed the fav'd bit on pictures! I haven't fav'd any photos yet but i can think of many that i will fave:-) None of mine have been fav'd yet but it doesn't bother me - tbh i cant say i have done one that deserves it!
Faving is really just a way to go back to them for whatever reason - I fav things I find beautiful, funny or just sweet. Lots of kitties, pups and other pretty sites :)
There was an earlier thread on this which may answer some of your questions: http://365project.org/discuss/themes-competitions/2649/i-just-absolutely-love-love-my-favourites
and here's another: http://365project.org/discuss/themes-competitions/2360/why-do-we-fav-our-favs