Recognizing and using E-Mail Accounts contact lists from yahoo, hotmail etc.

Privacy is going to be the issue here. If Ubiquity becomes, erm, ubiquitous ... it *will* be used for mischief.

Having social rating of commands is certainly helpful, but there are enough cases seen eg. in the Facebook app economy where an app gets popular by being fun and harmless, then becomes mischievous later.

Some months ago - and I still don't know how - some spammer got access to my entire Gmail contacts list, and sent a single spam to them all, with each address in the To: field. Not a pleasant experience :) If we don't come up with a privacy design here, more of that kind of thing is sure to follow.

My guess is that FOAF/XFN shared via OAuth is going to be one way this plays out... with Ubiquity commands (and other widgets) only getting access to certain subsets of the data (eg. URLs but not email addresses).