Few months ago Tweetbot was the first twitter client to roll out an update to include iCloud support for syncing the timeline position, dms and replies marked as read between the iPhone app, the iPad app (and the Mac app when it will be released).
iCloud offers a great way to sync data (even save games) between the same app on different (Apple) devices, but this simple solution is not used by anyone on the AppStore (apart from a few developers). I’m not a developer so i can’t really say if it’s because it’s difficult to implement or if there is another reason, but it’s a bad habit for the platform and my thought is that Apple is to blame.
Update: MacStories has posted an answer to my latest question, so be sure to check it out too.
Update #2: Also Instacast 2.0 implements it, it syncs with the iPad version of the app to keep the 2 libraries in sync. Clever.