Google mail, which I use fairly often these days, pays the bills by targeting its advertising to the text of the messages.
At first, this sort of creeped me out: Big Brother Google was watching. Soon I was amused by this computer-generated advertising, which sometimes made odd suggestions. And today, as I exchanged e-mails with my ex about her "parenting time" (a phrase I find meaningless....but I digress), Google attempted to direct me to websites with information for people who had abandoned their children.
How rich is that? Thanks, Google. I needed that.