I'm with Brit, I think they're downright silly. To each their own. I know we are judged as a group for having wardrobes for our babies.
I draw the line at strollers. Kaji needs the exercise and I pick him up for everything else. For shopping, walking in crowded areas, etc I pick him up. If I know it's dangerous and I can't take Kaji anyway, he stays at home. I was going to take him to Dodger stadium this May, and there is no way I'd take him in a stroller. It's a crowded place, and a stroller simply wouldn't work.