Out of the top of my head...

Nokia hosts MeeGo apps
Nokia goes bankrupt, or otherwise shuts down hosting for whatever reason
???????
Profit (for M$, at least)

Now, forgive me for sounding a tad too paranoid, or otherwise too negative... But considering Nokia's situation, I'd say that embracing a solution from them means, irrevocably, that a well-thought out backup plan should be ready to kick in at any time, otherwise chances are that they might drag a lot with them, when they go down...

Also, I'm not too convinced that Nokia's really interested in the well-being of MeeGo, after all that's going on. I'd take their offer with a bit more than a slight whole lot of caution. Much, much more...

Anyways, my two cents.