Having at least some knowledge of all the pertainant tiers is pretty helpful when sketching out an architecture for others to follow. When combining specialist

Having at least some knowledge of all the pertainant tiers is pretty helpful when sketching out an architecture for others to follow. When combining specialists, there's a lot of merit in having someone in a senior position who can speak everyone else's language. At smaller scale, strong full stack developers can get quite a bit done in "team of one" mode -- perhaps more than two specialists who have to spend a fair amount of time thrashing out interfaces.