November 8, 2011 - A company called Hothand sued the popular daily-deal website Groupon for infringing a patent on a "subscription-based system for providing commerce information for one or more mobile devices for one or more merchants".
Hothand claims that Groupon's iPhone and iPad apps infringe the patent, as do its apps for Android, Windows and BlackBerry devices.
Hothand also filed a similar suit against Yelp, a review site, and previously filed suit against Foursquare. In the Foursquare suit, settlement negotiations over the summer failed and the suit is ongoing.