Think it is harmless to push that "like" button on Facebook? Well, your face and comments are being turned into ads for the products you like. This article gives more detail on how Facebook has the right to do this.
Your friends will get ads for products with your face and comments formatted as an endorsement. Many companies have been encouraging "likes" to get discounts, or as sign-ups for contests. Personally, I found the begging someone to "like" you was a little demeaning. I feel almost like a middle school mean girl, deciding whether I like something or not. But turning my feeble like into an ad is like going to third base when I thought we were maybe shaking hands.
So now along with an "un-friend" button, we really need an "un-like."