But the thing is, if I check in at Starbucks all the time, and I "like" their facebook page, etc, what's the point of showing me their promoted posts? I'm already buying their products.
How will the fact that I like Starbucks tell Facebook when I'm in the market for a new vacuum cleaner? I might search for vacuum cleaners on Google, but Facebook is going to have no idea that I'm even in the market for vacuum cleaners unless I go and "like" a bunch of vacuum cleaner pages (which I presumably found by searching on Google).
If you check in at Starbucks, it's not Starbucks that would pay to talk to you, it's McDonald's. Just like Google, if you are searching "Starbucks", it makes no sense to show a Starbucks.com ad.
Don't sell the upsell opportunity short either. If you buy a lot of things at Starbucks, you could probably be more easily convinced to spend more on your next trip.
An 'ad' isn't the only activity Starbucks would post. We're in a less traditional paradigm here. Starbucks can do ad-hoc market research, community building, announce products... Lots of things.
Some of the other commenters build on this further through competitive analysis and predictive modeling. Over the next few years we'll see this go further as they better understand the cooperative nature of brands and likes.
How will the fact that I like Starbucks tell Facebook when I'm in the market for a new vacuum cleaner? I might search for vacuum cleaners on Google, but Facebook is going to have no idea that I'm even in the market for vacuum cleaners unless I go and "like" a bunch of vacuum cleaner pages (which I presumably found by searching on Google).