I think that that's an important piece of information that's rarely used. Like brlewis says, not perfect, but I think you could use it well. I think it's more

I think that that's an important piece of information that's rarely used. Like brlewis says, not perfect, but I think you could use it well. I think it's more suitable for a single site rather than a link aggregator/social news, because once you follow a link on the site, how do you know when the user leaves that page?