It was a sue day yesterday, on one side Microsoft sued Barnes & Noble for infringing upon its patents by using Android in Nook and on the other side Apple sued Amazon for AppStore trademark violation.

Microsoft Case: Microsoft filed legal actions in the International Trade Commission and the U.S. District Court of the Western District of Washington against Barnes & Noble and its device manufacturers Foxconn and Inventec Corporation, for patent infringement by their Android-based e-reader Nook. [Press Release]

Apple Case: In a complaint filed in California, Apple accused Amazon of improperly using its App Store mark to promote its “Appstore” mobile software developer program and the associated download service it plans to launch tomorrow.