On topic: sometimes. Sony have made some incredible purchases over the years - Psygnosis (kickstarted them in the gaming world), Naughty Dog (started small to become their #1 studio), Media Molecule (I reckon we're going to see even more creative & great things from them in the future).
At the same time, they've made some questionable decisions over the years imo. Buying BigBig seemed to make little sense. I'd argue Zipper and Evolution were just impulse buys as well.
Regardless, Sony's first party is stellar and has been for a number of years, so new teams joining them is always good. I love the infrastructure they have where they all seem to help each other out, as well as third parties, in developing their games.
edit: But yes, they need another Japanese studio. They should open one, rather than just buying one. Less money, but they could probably find some good talent around.