I do wonder how easy it would be for someone who has your business card to frame you... Is it possible to overwrite the OS on these with something malicious?
It is absolutely possible to overwrite the operating system. You have full root access when you log in. You can dd right over the flash device /dev/mtd0 with whatever you want.
As to framing me, well... I don't think it's much easier than framing me using some other method. And I think the cross section of people that want to frame me, and people who know how to compile Linux, is hopefully very small.
