keyplyr - 6:56 pm on Jan 8, 2012 (gmt 0)
While FB is blocked it does not prevent the visitor from viewing the page and voting.
During my tests, I blocked FB. I still got human visitors from FB, but greatly reduced (maybe 80% less) than when I removed the FB block. I attribute this to several things:
If FB blocked - when someone posts a direct link to my site, the link looks like a url. Plain and not very inviting.
If FB not blocked - when someone posts a direct link to my site, FB grabs an image from my site (the FB user is given several image choices and may choose which one) and a META tag snippet, making the link look very attractive. The FB user can even "feature" this post giving it larger presentation. This also increases the chances that other FB users will "like" the link and repost on other areas of FB.
There are several other ways in which a web site may get traffic from FB, but all are much more attractive presentations if FB has access to the web page.