You probably know that, on the Web, advertising is hardly the one-size-fits all model we came to know in print newspapers and network television. You know, for example, that if you're a thirtysomething and you're mom's a sixtysomething, and both of you are on Facebook, you get ads for Hawaiian vacations and Volvo station wagons while your mom gets ads for wrinkle cream and Florida condos. Because Facebook knows who you are (remember all that profile information you entered?) and serves up ads accordingly.

A new company Google just announced it's acquiring shows us how even more fine-tuned the ads that leap onto our screens are going to be in the future. San Mateo-based Teracent makes display ads for the Web (and mobile devices). But not just any display ads. Teracent's systems actually build the display ads on the fly, based on what it knows about the specific person it'll be shown to. So, for example, assuming both you and your mom have indicated you're interested in home hardware (perhaps you both did Google searches for Home Depot?), it might build the ad on top for you (since you also were searching for lighting fixtures) and the one on the bottom for your mom (because she lives near Colchester, VT). Automatically. In real time. Using what are called "machine learning" systems.

So the bad news is that the machines are, in fact, coming for us. The good news is they know what we like.