It's more the annotation/cropping feature set that would make it valuable. Currently to mark up a site, I need to go to that site, open skitch, take the snapshot, then edit it in skitch, then save. Then attach it to a gmail message and send (or upload to dropbox and send the link).

If there was a cloud solution that could do all of this, and provide a link that I could just send someone - it's just so much easier.