Because the tech community is NOT fooled by politics as usual and is not willing to put up with the phoniness and corruption that other traditional liberal voting blocs have become used to. Techdirt has a great article on the failure of the Obama administration to live up to one of its many campaign promises. What's truly important here is that they are cutting at the core of the Obama image and campaign: Change you can believe in. In essence, Techdirt knows the Change has not come, and they are not willing to accept business as usual.
This is critically important, but when you add this sense of disullusion to the natural free market instincts of the tech community as demonstrated here, you have a real recipe for major social and political change. Too bad it probably wont happen.