@roger,
NSA's mission is to discover and thwart attacks from foreign governments. Facebook's mission is to mine as much personal information as possible to sell ads to merchandisers for profit. And Facebook doesn't just pair up people who already exchange email, their algorithms mine the address lists of users. So I email my son, he emails his friends and then remarkably invitations to "friend" are sent out as if you were the one sending it. I have unfriended a cousin eight times, and within a week or so, she accepts my invitation to be "friends".
Visit an online store and wait for the pop-ups to start crowding your screen.