The Seattle Post Intelligencer has the by far best analysis on the "Mono BOF" at the PDC - read it here (Builder UK article for contrast). From the marketing aspect of the BOF refusal to the impact Mono will have to shops that bought into Windows (zilch, that is), those two articles cover all bases.
Especially the one I also like to point out: Mono will always play catch up with .NET (unless the development pace at MS slows down, but there was no such sign at this year's PDC). I had to laugh out loud when the Seattle PI quoted Somasegar as saying that "it's [Mono] a good science experiment that is happening there". And a warning that if it eats into their revenue, they will reconsider their current position. Given that Mono not only implements the ECMA standard, this certainly is an option. Taking further into consideration that MS sure as hell won't risk a class action suit from shareholders growling about lost money because of Mono, this is a threat scenario the Mono project better prepares for.
Before you flame me for the previous paragraph: I am project manager on the open source #develop project, so spare me the FUD blames. Especially if you are IANAL.