LOL @ lulzworth, that's awesome.
Keep in mind that your profile would have a list of all the aliases you've ever had, and it'd be time-limited to about once a year, so people couldn't do it often. And like Ursa said, you wouldn't want to give up your points if you had an established account, so you wouldn't want to close your first account and open a new one.
Other rules that could make it work better would be the following, although you wouldn't necessarily implement all of them:
1. You can't join and then instantly change your name, you have to be a member for a year before you can make the request. In effect, the only people requesting name changes would be veteran players with a vested interest in their points and reputations.
2. Give the name change a price (either set, like 100 points, or on a sliding scale, like 10% of your current points, including those tied up in games). You can only make the request if you have enough points open. This discourages username horseplay.
3. Automatically disallow clone accounts. Simple permutations of current account names would be disallowed, e.g. fortknox2, vamosramstein, jman778, Dingleberry Jones (note the space), etc. Currently, someone could make a new account with any of those names, and I'm not sure how the mods would handle it. It might be difficult to enforce, unless...
4. Publicly present each name change request in the forum so that users can voice concerns and complain pre-emptively. If someone named Dunecat decides sand-burrowing is passé and instead wants to become GordonFremen instead (get it?), anyone would have the opportunity to speak up in objection in case there were a player named Gordon Freeman, for example.
5. Require moderator approval. You can only request a change, and it's entirely up to the discretion (and whims) of the mods. If anyone tried to change his name to lulzworth2, they could deny it, and whoops, you just wasted your annual attempt. Hell, they could even deny changes they just didn't like.
I think any combination of the above rules would keep it under control.