It doesn't, the running-in-the-background thing is about the only type of multitasking we'd ever need unless we developed an IME (and that requires OS-level support in other ways anyway). And it's the only kind we'd get on iPhone too unless we start supporting background audio playback (though that's certainly a possibility in a future version if we add some new specific audio learning features).
That being said, with HP buying Palm I think the prospects for Microsoft in the mobile space have just gotten a lot bleaker - webOS does basically the same thing as Windows Phone 7, offers an web-code-based API for regular apps and a native-code one for games and processor-intensive apps, but it does it using nice open standards, is if anything even more accommodating of unsigned / un-approved apps than Android (while WP7 seems unlikely to run them at all without hacked firmware), will have a year and a half of extra maturity / mindshare / feature additions by the time WP7 hits, and will have a hardware manufacturer putting it front and center - most of Microsoft's other launch partners are very much in the Android camp and aren't really committed to WP7 anyway. If anybody other than Apple, Google, or hanging-on-in-spite-of-their-continued-mediocrity RIM is going to carve out a corner of the smartphone OS market, it's probably HP / Palm. The only thing Microsoft really has going for them in this battle is Office, but I have a hard time thinking DataViz or QuickOffice or one of those guys won't have a very solid webOS version out by the time WP7 hits.
That being said, with HP buying Palm I think the prospects for Microsoft in the mobile space have just gotten a lot bleaker - webOS does basically the same thing as Windows Phone 7, offers an web-code-based API for regular apps and a native-code one for games and processor-intensive apps, but it does it using nice open standards, is if anything even more accommodating of unsigned / un-approved apps than Android (while WP7 seems unlikely to run them at all without hacked firmware), will have a year and a half of extra maturity / mindshare / feature additions by the time WP7 hits, and will have a hardware manufacturer putting it front and center - most of Microsoft's other launch partners are very much in the Android camp and aren't really committed to WP7 anyway. If anybody other than Apple, Google, or hanging-on-in-spite-of-their-continued-mediocrity RIM is going to carve out a corner of the smartphone OS market, it's probably HP / Palm. The only thing Microsoft really has going for them in this battle is Office, but I have a hard time thinking DataViz or QuickOffice or one of those guys won't have a very solid webOS version out by the time WP7 hits.