I think it might make sense for Twitter not to show ads to people who they want to stay engaged. Similarly I think people who post lots of links, curators you might say, should be immune to paywalls. I always think it's stupid for the Chicago Tribune to block me, when there's a good chance I'll post a link to the article I came to read. I'm certainly not going to pay to read the Tribune, I don't live in Chicago, or follow any of their teams regularly (unless the Mets are sweeping the Cubs in the NLCS). The Boston Globe too. I actually pay to access the NYT through their paywall. I bet I make money for them because I post so many links to their stories. Not that I'm trying to do that, I don't care if I do or don't. But it's kind of silly to make me pay for that. But for my local hometown paper, I do.