I've been on the front page a few times and got around 10,000 to 20,000 visits from it. It often brought many more comments on the posts that made it than when people find it another way, but I saw no real increase in social sharing. Opposite that, if a post makes it to a fairly popular subreddit, I get a lot less comments from that kind of traffic, but on the other hand the posts will tend to be picked up again by other blogs or sites. I found that interesting.