Oh totally true. But coming up with a few more tedious Twitter cleanup type activities might make it an offering that is more valuable to more people! (While adding minimal cost)
One idea I've thought about is allowing users to download the tweets they're going to delete in one file format or another. I imagine there's some extra value I could add in there somewhere as well... am just not sure what ;)
Suggestion: Download is great, email might be better.
I don't get many DMs on twitter, but if I did I could see an automated "clean out everything over a month old and email it to me" service being worthwhile.