I have added a new feature to my new service (http://copyto.co) which lets you have discussions on your public clipped pages. I just wanted to have your opinion about this functionality and whether you think if it would be useful. Thanks!
I think Disqus is a good choice for the comment system. There are some issues with the frames when I try to login to my disqus but other than it looks nice and I think can be used easily to collaborate.
