Another feature I think would be really cool in a tool like this is that it could auto-discover which feeds you read often, even if you haven't subscribed to th

Another feature I think would be really cool in a tool like this is that it could auto-discover which feeds you read often, even if you haven't subscribed to them. If it detects that you visit blog X often (either deliberately or from being redirected, tweets, etc.), it could recommend that you subscribe.