Nokia were failing through lack of commitment. I believe they had a killer O/S in Maemo, they just didn't have the vision or the motivation to take it further and improve on it.

Microsoft were in the same position with Windows Mobile. They lacked the vision, commitment and motivation to take it further.

Both parties were losing out to Google big-time. And it's no surpise because Google were literally giving Android away. It's obvious manufacturers were going to jump ship. It's been the view of almost every technology firm for the past decade or more that "If you can get one for nothing, why pay for the alternative?"
Microsoft saw a big money pit and jumped in, end of. Anything that Elop or Ballmer says to try to avert attention from that is bull. They knew where it was going.

You know, I've looked at Microsoft's roadmap on this and it spouts on about Microsoft Adcenter too many times to make me feel comfortable.

I simply can't imagine anyone who lives in a rural area where 3G/3.5G is none existant grinding their way through ads before they can get to the homepage to find more waiting in the wings.
I don't want that, it's my bandwidth, I pay £5pm for 1GB (way too much money IMO, given the state of the network) of course I'm going to want every drop of that 1GB for my own use, not for some plonker of a consultation company to tell the guy who's gawking over my shoulder on the bus that Robin Emblind Insurance is better than Bodget & Scarper.