i read somewhere (sorry, i can't remember) that USPS sponsored a team specifically to raise awareness of their services in europe... i have no idea what they're selling to the europeans (maybe they act the same way as a fed-ex or ups there?), but that was their marketing strategy for a long while. sponsorship seems like a bargain when you compare it to what a major advertising campaign might cost to do the same thing. i don't know if it paid off for them, but it sure has paid off for trek! in any case, it's no longer their strategy.
as an aside, i bet that discovery took up the main sponsorship not because they wanted a bicycle racing team, but because they wanted lance. not only did they buy themselves a hero of a spokesman, but a someone to host their programs that is already loved (and hated, but always watched) by half the world.