Glyfair
Explorer
I was about to same the same thing as scribble. I have played a number of "classless" system and have seen it often, but not always.And it really doesn't come even remotely close to my own experiences using classless systems, even in those campaigns that have included some 'optimiser' types.
I typically see it controlled by two things. First, is the players themselves. If you don't have optimizers, or the group tends to frown on that sort of thing, it's not a big issue. The other are campaign rules to limit the customization of the characters (Champions was big on that).
However, in my experience the more options for players, the more hooks for super min/max optimizers to dominate the feel of the game. It's inevitable that the options will be there, even if they aren't used.