Description length restriction

Is there a specific reason for the length restriction on the links descriptions? And if there is, and you’re keeping it that way (hint hint), is it possible to prevent the user from typing in more than it will take, so that it doesn’t delete part of the text?
A pretty cool system for showing how much text is allowed can be found on the blog on this site, go into comments and post a new comment and start typing (you don’t have to post to see it working).