It seems a lot of the discussion on this thread revolves around optimization and how the designers can handle that.

I wonder, when did this phenomenon of optimization first start? Has it been a part of the game since the outset? Or has it really taken off since the rise of the internet (and boards/forums on optimizing builds) coupled with D&D 3.x, with easy multi-classing and a 100,000 PrCs?

I honestly don't know the history of high-power gaming. My guess would be that in 2nd Edition and earlier, it was less of an issue. Sure, you had character kits and such, but nothing really like the PrCs of 3.x, plus it was much harder to reach out to the gaming community and get feedback on character builds back then.

I think WotC didn't anticipate how powerful an element of the game optimizing would become when they first released 3.x, because no-one really understood the impact the internet would have on gaming, especially a version of D&D with 100,000 PrCs.

Now it looks like they are trying to put the genie back in the bottle with D&D Next... it seems like it will be difficult.