We’ve updated the web platform to include the ability to comment on files, which works over any cloud. We shall shortly be rolling this into our Windows tooling and also into our mobile tooling where file comments will trigger push notifications to iPhone/iPad, Android, BlackBerry, if a user is subscribed. Currently users can subscribe to be notified for file comments via email.
File comments works on all files, but of course of single user accounts only makes sense if you are sharing a file with a business group. For our business Organisation Cloud users, file comments of course make a lot of sense and users can subscribe for notifications on files from Organisation public folders.