One of the most important lessons I learned from MUSHing (for the unfamiliar, think of it as LARPing online) is the power of weakness. People play games looking for chances to be awesome, but in a game where you're interacting with other players, that creates few opportunities, because everyone else would like to be awesome too. In this environment, the weakest characters were the strongest.
Howso? In this case, I mean 'weakest' in terms of most likely to fail. Some tiny element of this was related to stats, but the vast majority of it was a function of player attitude. In a basically cooperative environment, there was not much you could do to FORCE someone to lose, so the person who was WILLING to lose was a treasure. Immature players who didn't realize this abused it, and mysteriously found themselves unable to find play. For everyone else, the guy who was willing to lose became an incredibly valuable asset, especially if they could lose well. Someone who played a powerful character who was willing to lose? Solid gold.
Now, a cynic might deride this as metagaming. The player who is willing to lose is getting numerous rewards (social esteem and more play, most notably) in return for the willingness to lose in fiction. Personally, I think it's a more than fair trade, but it's worth noting that this does involve thinking about the game (and the satisfaction of play) on more than one level.
Now, that's great for large-scale, multiplayer play, but what's interesting are its implications for tabletop. While this lesson does not translate directly, the multi-level thinking behind it does translate very well, and provides a specific sort of incentive for weak characters.
Now, weakness translates a little differently on the tabletop. Some of it is character power, but there are also elements of making your own life harder. Whatever route it takes, the purpose is a character who easily gets in trouble and can't get themselves out of it, thus providing play for the rest of the group. Again, the player is making a tradeoff - they're sacrificing optimization for the ability to direct play, to be at the center of things and in some cases, for attention.
Now, this is not always a good thing. It can be obvious attention-getting behavior, and when that's what's going on, it can be very frustrating to the rest of the group for obvious reasons. But in small doses, it's highly desirable behavior - it's something you want from everyone in the group ideally. In many ways it's the opposite of the stereotypical orphan-loner.
But here's the rub. Once players understand that their weaknesses pay out like this, the very idea of game balance gets dragged out back and shot. Trying to balance a game on a single axis (like combat capability) becomes amazingly short sighted once players are thinking about play opportunity, spotlight time and game direction. This is not bad in its own right, but it becomes bad when you have mixed understandings at the table. If only one player understands this is what's going on, then he's going to play Tyrion Lannister and all those big strapping knights are going to have no idea how they keep getting overshadowed. If you're lucky, your Tyrion is really trying to help the rest of the group, but if he's not, then god help you. Every argument you've ever had about game balance will get turned on its ear and used against you if you protest.
All of which is to say, be careful, keep your eyes open, and try to make sure everyone at the table has the same idea of balance, at least in broad strokes. It'll make for a better game all around.