...while Twitter and Facebook are free.

And they require almost all articles to be posted on HN. I have a feeling majority of their (click) traffic comes from HN.

It would be nice of there was a limit on how many articles from same domain can be posted on HN. Nytimes articles in my humble opinion are listed here too often. Or a rule that you cannot post paywalled content. It's becoming quite frustrating when you click a nytimes link.