Brendan Trotter typed:
A much better idea would be telling the retailer "Screw you, I'm buying a motherboard with coreboot pre-installed directly from coreboot.org because none of the products you sell mention coreboot compatibility and I don't want to end up with something that doesn't work". Retailers don't care why they made a sale as long as they make a sale, but they do care about lost sales.
On the main page http://www.coreboot.org/ which redirects to http://www.coreboot.org/Welcome_to_coreboot there's lots of information but I see no "get coreboot" anywhere. Maybe coreboot is still in its infant stages to go so boldly forward yet.