This. There aren't enough dead single reponsability horses :P. This should be drilled in new and experienced programmers over, and over, and over again. And then some more. Because while it sounds so simple it's actually all to easy too violate and because it applies to each and every layer of a project. I'd even say most design patterns are actually proper implementations of SRP in one way or another. Most of the time I have a feeling something if off with my code, it boils down to some pieces just doing too much, hereby dragging others down with it.

Anecdote applied to this particular topic: the intern, proud of having used composition as much as possible, creating mostly classes composed of 10+ other classes and functions that might as well be called NowDoItAll().