Facebook plan introducing a service called "Sponsored Stories", which is where when users clicks a "Like" button or comments on a company's product, the company can create personalised ads based on this information to show to the friends of the person who commented on or liked the product. This apparently is more effective than just showing generic ads. Users will not be able to opt out of this service.
I was wondering what this "Like" button was going to be eventually used by and sure enough, this doesn't surprise me.
See this C|Net article for the full story.
Sure... So what happens if you delete your Facebook account?