For some reason, Facebook seems to think that I need an engagement ring. They use demographics to help people who want to advertise on their website to find consumers to target their products to. I have been in a relationship for 2 years and since Facebook knows that, they sell my information to engagement ring company's who advertise on my page so they can plant the idea in my head that I need to get engaged. This could also be seen as an example of market fragmentation, as they divide the college age market into people who are single and in serious relationship, but not yet engaged so they can market their products to people who might actually want them. Two years ago, before I was identified as "in a relationship" on Facebook I never saw ads for rings.
Facebook also has me labeled as a student, as you can see, VISA is marketing a student credit card to me they've even colored pink because I'm a girl. Based on the design of the credit card, it looks like VISA's segment profile has college girls pegged as all being in a sorority and thus wanting a pink and silver credit card.