Feature wise FB may be ok, but from the user experience perspective they have failed to offer anything remotely attractive on the mobile. This is what makes apps like Path and Everyme attractive, they were designed with mobile in mind.
Plus their mobile platform straight up sucks. It takes ages for mine to load (on iphone 3gs) on wifi or 3g. Even then, some of its capabilities are hobbled. I was trying to do something the other day (i dont remember what), but was very frustrated at not being able to do it.
