I would suggest only asking the second time people land on your site. The first time, they're probably not going to do it, because they just came in via some article link and are thinking they probably won't see your site again.

For sure. Well, I unblocked the site while reading, so I guess the scale tipped over to appreciation.

Although, I'm skeptical about the Facebook/share buttons. It'd be great if they didn't load content from the sharing sites themselves automatically (as they can track who is reading what by looking at the requests and referrer).