I think Twitter is the open commenting system for the web, in a different form factor: the comments box is centralized and you need to include the URL of the page you are commenting on. This has much lower "activation energy" (great term!) because of stronger ties with people who see your comment (classic social network effects).
An interesting path to go down might be to search for these "comments", filter+rank, and show them on your webpage.
Product reviews seem to be in a similar situation (I think?) except Amazon has strong incentives to maintain tighter control on their reviews.
I think Twitter is the open commenting system for the web, in a different form factor: the comments box is centralized and you need to include the URL of the page you are commenting on. This has much lower "activation energy" (great term!) because of stronger ties with people who see your comment (classic social network effects).
An interesting path to go down might be to search for these "comments", filter+rank, and show them on your webpage.
Product reviews seem to be in a similar situation (I think?) except Amazon has strong incentives to maintain tighter control on their reviews.