@Outlook team, how about Ctrl+A shortcut for "To", "Cc" and "Bcc" fields to "Select All" contacts in Outlook web and metro app. Subsequently pressing backspace should remove all fields. Here is the demo:

http://jsbin.com/UTEBozA/6

The behavior is inspired by the tags field on http://stackoverflow.com/questions/ask Enter few tags and then press Ctrl+A.