TwitWipe gives you that fresh start you always wanted to have by removing all, yes all, of your tweets. There is no archiving with this tool, the writer really means that it simply deletes everything and gives you that fresh start. Now I did find a conflict in one of the description paragraphs below:
Why not just delete the account and create a new one?
Doing so will create a new user id (the numeric id). It’s going to be a separate, new account. All your followers and followees and flurries will be gone! That’s why you should use TwitWipe, because it lets you keep all your followers, favorites and the people you’re following. If you’ve signed into any apps with your account, TwitWiping will keep all that intact. It’s like that memory eraser pen from M.I.B.!
As you see, in one line it says followers and such are gone too. The next sentence says they stay. So you have been warned if you lose followers.
It will take some time to run depending on how many tweets you have, so patience is a key in using the tool. They recommend you leave it running overnight as necessary. The site uses oAuth so no password information is stored and they joke that there should be no big deal, it is deleting everything anyway.