So Facebook is now totally a thing and marketers are all over it because it lets them invade the privacy of average consumers that much more and because it gives them an objective, but thoroughly meaningless, number that they can pretend represents their "popularity" or summat.
Facebook does a lot of things for marketers— it somehow manages to convince people to dump their private lives and private information into the clutches of a company that explicitly exists to abuse it, creating a vast wealth of information about who's interested in what, and allowing marketers to attempt a form of ad targeting that's less bullshit than the normal cookie-based educated guesses— to target ads based on the kinds of products people express interest in and therefore might be in the market to buy. You'll notice I said "attempt," not "succeed" in that sentence. That's because, while Facebook has been quite successful in getting people to disregard all notions of privacy with respect to their lives, they haven't solved the fundamental problem that computers simply can't derive someone's interests from their activities with any level of precision. Sure, you can try keyword matching and various tricks like that, but it's still just educated guesses— the same kind of "targeting" you get from a tracking cookie. They have all the data, but no way to interpret it.
Facebook tries to work around this problem by implementing the "like" button. They figure, "people are willing to make us privy to all of their private information, maybe we can make them do the work for us by explicitly telling us what their interests are in a manner we can readily interpret. So, we give each company that wants to market through us a big fancy "like" button, and allow the users that like them to register this approval!"
The first problem with this is that real humans do not genuinely like companies, so the entire concept makes no sense outside of the marketers' fantasy world where people emotionally connect with legal fictions and small pieces of intellectual property.
The second problem is that even if there are a few subhumans out there who define themselves by what brand of crisps they buy, Facebook has transformed the "like" into a supposed measure of popularity. Companies are desperate to be more popular than their competitors, and therefore desperate to get more "likes." This leads them to pursue more effective ways of gaining "likes," namely by paying money for them. Most companies will, at minimum, offer a discount in exchange for your willingness to click the "like" button, with some paying cashy money to buy bulk "likes" from dummy accounts, thus completely defeating the supposed purpose of the "like" button and turning it into a measurement of how much money you have invested in purchasing "likes."
But the "like" system resonates with marketers in no small part because it reinforces one of their prime delusions— namely, that people can genuinely like a company and thus hold loyalty to it and its products, and especially its brands. Accordingly, marketers become quite invested in the whole Facebook thing.
And so, a recent market research survey asked: "What percentage of your Facebook friends have you met in real life?"
That I wasn't on Facebook never even occurred to them.