Well, there is a key similarity in the two moves.

In Google’s case, the consumer-facing company offers online maps, and is doubtless buying ImageAmerica so that it can offer richer layers of image data on top of those maps.

In TomTom’s case, the consumer-facing navigation products company is hoping to buy its main map supplier, so that it will control both the device/navigation layer of the customer experience, and the very important map layer. (As an added benefit, TomTom might be snatching an important supplier away from its competitors at the same time.)

Both point to an interesting trend. Digital maps are becoming a more important part of the way consumers interact with information. The trend is starting with in-car navigation systems and in-browser location searches – but it’s not difficult to imagine that mainstream cell phones could soon have built-in map applications and GPS for offering convenient location-based services.

The iPhone’s implementation of Google Maps is just one example of where things are headed; Zillow’s use of Microsoft (MSFT) 3D mapping from Pictometry provides another view of what’s possible. (Real estate is one of those categories where digital mapping could become an even more valuable part of the buying and selling process.)

There are all kinds of revenue possibilities, too. Yahoo (YHOO) has begun to sell map-based ads; pull up Yahoo Maps from a broadband connection, and you’ll see the option to automatically display businesses like Holiday Inn, Fairfield Inn, Sprint and Goodyear. You can imagine that when mobile phone maps truly go mainstream, Starbucks ads will be (ahem) just around the corner.