best app I've found that let's me backup my files, essentially my social diary. I lost it all once who xanga when they ran maintenance. now I have all my tweets an fb updates posted in case someone hacks my accts OR the server loses the data.
This is such an interesting idea- it's kind of like a portable, electronic diary. I know a lot of people who would use this. People carry around their iphones all day, all the time already and most would appreciate a quick and easy way to record the day to day events in their lives. It'd be fun to look back on random dates through the years.
Momento is a very well designed diary app, that aggregates your activity on social networks daily and presents in a very nice format. So I can go to last Friday and see my tweets, the tracks I loved on last.fm, the pictures I uploaded to Flickr or Instagram, my Foursquare and Gowalla check-ins etc. Not super important but kind of nice to look at it every now and then.