This feels like a PR-disaster in the making. McDonalds have been running a campaign around a tale of some small town American discovering a chip that 'looks' like Abraham Lincoln. There's even a blog. Thing is, according to Kevin Dugan's PRBlog: its all a fake.
I don't know how many people visit Dugan's blog - more than this one, I can confortably guess - but the real impact occurs when it hits an überblog like Gapingvoid with hundreds of thousands of hits a month and the influential likes of Jeff Jarvis and Tom Peters having a look: überblogger shall speak unto überblogger and the rest of us parasites feed off them.
As Malcolm Gladwell famously demonstrated in The Tipping Point: one link to a hub, and an idea spreads. Very fast. If the idea is 'McDonalds is faking', then the company loses trust. If the company then tries blogging again they have first to overcome the trust discount.
Blogs are an opportunity for openness and conversation: missing this opportunity is an own goal. Doh.