I like the idea of the built-in share buttons, but I was dismayed to learn that they share cookies[1] with the main browser pages. I consider the share buttons that are on pretty much all websites a privacy drain because they send data on the page you're visiting to the social network whether or not you choose to share it. So I ensure I'm not logged in while browsing normally, and only log in when I want to share something. If the firefox share services used separate cookies (I guess like private browsing must), then it would be a really handy feature. 1: https://blog.mozilla.org/privacy/2012/10/22/being-social-with-privacy-in-mind/