I agree that paid advertising for free sites is a difficult proposition, return-on-investment-wise. But if you have a "sticky" free site where you get loyal return visitors, it may be worthwhile. Your personals sites are sticky, so if your motive is to grow and you can afford it, buy some high-exposure advertising; don't expect immediate return. (I don't know which paid advertising would be best for you.)

Have you used all free-advertising options available? I know you do link exchanges and link lists; but how about banner exchanges, small-free sites, AVS sites, and TGP gallery pages (these can bring in lots of traffic) all to promote outboy?