A number of accessory makers have launched new offers aimed at taking advantage of Apple’s recent announcement of a free iPhone 4 case offer. Both Incipio and Proporta are offering Bumper trade-in programs, with Incipio promising $5 off any Incipio product for each Bumper sent to the company—a limit of two per household applies—and Proporta offering 20% off any Proporta case or screen protector for the iPhone 4 with each Bumper returned…
