If there are rules, there is optimization!
But some systems DO make it easier on you. d20, by being so incredibly rules-oriented and releasing, in every new book, unconnected and badly un-tested (by anyone knowledgeable about rules in OTHER books) mechanics, invited abuse beyond what many other systems could.
In other words, though optimization can happen in ANY system, it's probably only complex and entertaining enough to spawn entire forums in d20!
Well, maybe not ONLY. But close to! d20 has invited optimization on the level at which MMORPGs like Diablo II and others have - in effect, a massive, microscopic inspection of how the rules work which allows people to find loopholes to exploit. Better yet, rather than having hard-wired rules with predetermined outcomes (as in a computer game), it's based on interpretation of language and implementation by individuals (gamers), leading to all sorts of fun linguistic loopholes and semantic games that can be played to break things even further.
Which is why CO has become such an interesting entity in d20, and, I'd argue, should be as fundamental to its brand and product image as the 20-sided die itself!
Hmm. This little rant may warrant a post on the WotC boards. Things seem to be stirring in the pot over there, and this spice might add something to the mix.
Thoughts?