Just ran across Stormpath [1] in a recent mailing [2]. They provide a hosted user management service instead of you having write one (using Devise and CanCan, for example). Has anyone used them or anything like them? What do you think about off-loading your app's authentication and authorisation to a third party?
[1] https://www.stormpath.com/ [2] Advanced User Management for Ruby, Rails and Sinatra