Raise your hand if you like the Facebook Like button! ... yeah didn't think so.
http://blogs.webtrends.com/blog/2010/05/12/think-before-you-like/ describes how you're giving away permission to post stuff to your own news feed
http://bit.ly/fblikeperfisbad (see Act Three) describes how the FB Like button is terrible from a page performance standpoint.
Install here (extra points for pronouncing the URL)
You can also install it as a greasemonkey script in Firefox by renaming
likeblock.user.js and opening in FF.