If I happen to FAV your work(s), you don't FAV me back unless you're reaallyy, I mean reaaally like it.
I FAV your works, because I LOVE them, no ulterior motive of having a FAV back whatsoever ( it sickens me :D )
You just need to keep up your great works to 'thank' me. Your works inspiring and somehow 'entertain' me.. so I show an appreciation by fav-ing them. :)