It looks like Apple has just started sharing status updates with an official @AppStore account on Twitter. The account isn't verified yet but its first tweet has been retweeted by the already verified @iTunesMusic. So why is the App Store on Twitter? Well, according to the first public message:
Welcome to App Store on Twitter! Follow us to discover new apps, get exclusive offers, and share with friends.
It will be interesting to follow the tweets from this account closely and see if they mirror the apps Apple features every Friday on the App Store homepage. This new account expands the set of official Apple services and personalities on Twitter.com: @iTunesMusic and @iTunesTrailers tweet new material from the iTunes Store on a daily basis and @pschiller has been busy sharing Instagram pictures lately. Apple is also active on Facebook and Youtube, where all the commercials and keynotes end up in HD.
On a side note, Scott Forstall hasn't tweeted yet.
Update: the account is verified now. [Thanks, Florian]