Hm. Why would Tom Tom joining OIN cause Microsoft to back down when MS is not part of the network, and with the network having no retaliatory powers?
(Speaking of retaliation, I have this dream of a patent-holder going all the way and forming a Software Patents Mutually Assured Destruction patent pool, its members forced to leverage their patents to the greatest possible extent against anyone launching a "first strike" software patent suit. With enough momentum, such a pool could force non-members to join by threatening to sue, thus growing katamari style. Considering that nobody has done this yet, I gather that even the companies most critictal of software patents see a value in them.)