Google's advantage is that people use it to find things they want, including things they want to buy. A user who is searching for "hiking boots", for example, i

Google's advantage is that people use it to find things they want, including things they want to buy. A user who is searching for "hiking boots", for example, is valuable to an advertiser because they are actively seeking information to make a purchase, and a sponsored link might be exactly what they're looking for. Conversely, people use facebook to chat to their friends. They don't use it much to make purchasing decisions. So advertising there is less valuable, because people aren't necessarily in a buying mood. This is why facebook needs far, far more data on you as an individual - what you like, what your friends like - to advertise to you effectively. Because you're not telling it what you want - as you do with google - it has to guess based on what kind of person it thinks you are. I'm sure facebook will have a lot of success with advertising - TV does okay, even though people aren't trying to buy things while watching their favourite shows - but I don't think they'll be beating google.