I dont tend to browse another persons favourites as much as I do their Gallery however If the deviant or group has a favourite on display that catches my attention, sometimes it makes me curious to browse through the rest of their favs. hence why I do at times.
I browse peoples favorites rather frequently. If someone favorites my work I will browse their favorites to see what other art they like as well. If I like an artists work I will browse their favorites to see what kind of art they like. It's very interesting to see the different collections people have and make, and what types of art people like etc. Very fascinating stuff for sure!
Not all of the time, but I've noticed that if I'm on the page of an Emoticonist or someone who creates a lot of character based work then I'll have a look through their favs/collections to see if I can find any new artists to watch and be inspired by.