One argument for app.net appeared to be "controlling my own data" so I thought I would point people toward what Twitter has said about giving users the ability to download all of their tweets soon.

I hope they deliver but I'm not too worried about it if they don't. I currently archive my tweets using IFTTT: Delicious.com for the ones with links (http://ifttt.com/recipes/332), Dropbox for the whole stream (http://ifttt.com/recipes/37991).