They don't sell secrets about your life, they allow advertisers to target ads based on demographics, location and categories of interest. This does not mean they say "Hey advertisers, Jane Smith likes to do drugs with her friends and take embarrassing pictures. Sell her stuff!". It's more "Show my ad to women between the ages of 18-24 in Portland, OR who have an interest in rock music". It's just boring, not evil and not an invasion of anyone's privacy. Mailing lists have been segmenting audiences for decades, often with much more personal information, and no one is freaking out about it.
The facebook model of advertising is stupid anyway. They have the potential to use unimaginable amounts of information to infer who is most like to buy what from whom. Instead of using it to the fullest extent, they let advertisers select their own targeting criteria based on tiny sample sizes and gut intuitions about who their ideal customers are. You have nothing to fear from this, it's just advertising, same as it's always been.
If you don't like using facebook, just don't use it. The sky won't fall, the dead won't rise and the sun will come up tomorrow. They aren't doing any more harm than any other corporation, and the use of their product isn't any more requisite than any other product.