Indeed. And I've thought many times about it but never did it.

I did find a really great trick, though.
I originally setup my mobile in the alias file as "55555555555@txt.att.net", and I had the same thing you guys have: A billion text messages in separate conversations from incrementing numbers.

My colleague, a former cingular customer who recently bought an iPhone, never updated his alias. And his alert messages come through one number and into one conversation.

I never had cingular (was a vzw customer), but the alias "5555555555@mobile.mycingular.com" still works for me. And now all of my alert messages come into one conversation instead of many.

Hope this helps some folks out. I'd still like to see your app in the store, as I wonder how long it will take cingular/att to squash this loophole. Or not. But it's still a possibility.