A handful of iOS developers received letters this week from a patent holding firm claiming that their applications that offer in-app purchases infringe on the firm's intellectual property (IP). The letter threatens legal action if developers don't license the patent within 21 days. Lodsys, the firm in question, has apparently patented a system that collects usage data and facilitates feedback between a customer and vendor, though it doesn't address financial transactions specifically. The allegedly infringing applications use Apple's in-app purchase tool to encourage users to upgrade to a paid version after downloading a free app. Though it's possible that Lodsys has sent a similar warning to Apple, only individual developers
