Ever notice as soon as you search for something online, or click "Like" on a Facebook post, you suddenly start seeing ads for those very same things? It's called targeted advertising and it happens when websites collect your surfing history and use it to send you ads about things they think you'll be interested in - and maybe even buy.
There's an arms race among targeted advertisers to try to guess your interests based on the pages you visit or the terms you search. Some people may even think it's a little creepy the way targeted advertising can get into your head and begin trying to sell you products and services.
But trust me, it's all due to clever little computer formulas called algorithms that can predict your interests based on your Internet habits.
However, what if a targeted ad knew things about your life that can't be accessed online? I'm talking about deep, personal things that only your closest friends and family know.
That's the idea behind one elaborate and hilarious Facebook prank between roommates.