I believe there should be a limit on the amount of smilies people use on posts or messages. The reason being is that when someone puts a large amount, the page lags. This is also really good for visitor messages. I'm unsure if this is possible but it would be a great help.
Well there's limitations on that if it's hurting someone. While it may not be a physical kind of damage they're doing (though the frustration it causes can sometimes result in that, haha), I've fallen victim to the "someone decided to add a million smiles to their posts, making my computer basically implode". If it's at all possible, I don't see why not.
As far as I know, this isn't possible without a mod of some sort... and I have yet to come across one that limits the number of smiles per post.