Whrrl, a competitor to Austin mobile check-in and social networking service Gowalla will shut down, after it was acquired by daily deals site Groupon Monday. According to Pelago, operator of Whrrl, a direct competitor to Gowalla, it has been acquired by Groupon, and will be shutting down its service. Financial details of the buy were not disclosed. The acquisition means one less competitor for Gowalla, which still has direct competition from mobile check-in firm Foursquare, plus similar features from Facebook Places.