Quite confusing why they aren't joining the Open Cloud Manifesto, I don't see why not.

Not sure. I just read through the version at http://www.scribd.com/doc/13710927/Open-Cloud-M... and it seems harmless enough, but I suppose the parts that both Amazon and Microsoft don't care for are things like "Cloud providers must not use their market position to lock customers into their particular platforms and limiting their choice of providers." -- sounds good to talk about but this is, after all, a key goal in maintaining market share.