the companies the you "like" SPEND money to advertise. Their ads, which are tailored to specifically to you, based on your information, come through your news feed. This is a very specific type of advertising meant to appeal to the consumer rather than annoy them. Most people can't wrap their heads around the idea that advertising can be non-intrusive and not annoying, because it has never been done like this before
I don't need to block ads on Facebook because they are from things I "like" durrrrr. How hard is this concept to get. That you can actually like, "like" an ad. But the best thing is that it is so genius that idiots can't even wrap their heads around the concept!! how can you like an ad? Easy, if you like the product. Then ads cease to be annoying as traditionally presented randomly and untargeted.