The operator of course. They are definitely useful (at least on our end). We've found that making it easy to share the blogs increases the odds that folks actually boink the button and add a personalized message. Plus the share counting works as "social proof" for posts. If you read a blog post that 3 other people have shared you might abandon it before finishing. If 300 people have shared it, you'll likely be more prone to finish searching for why they thought it was so interesting.

That can be gamed though, but we keep ours "natural".