In theory, the ease with which technology companies can enter new markets should be good for competition. With low barriers to entry, competition becomes more likely, and prices fall, to the benefit of consumers.

But in the case of Google, the situation is a bit more complicated.

Because it dominates Internet search, Google has the power to use its position to help it enter other markets. And its power is unique: While other companies like Apple may have more cash, only Google can make competitors effectively invisible on the Internet, at least in the U.S. and Europe.

Google insists that it doesn't use its power for evil. A few of its competitors have been arguing otherwise, and these claims have gotten the attention of regulators in the U.S. and abroad. This week, Google chairman Eric Schmidt will face a Senate panel on antitrust issues, with executives from rivals including yelp expected to testify.

But regardless of whether Google is competing fairly or not, many companies fear Google entering their markets, particularly if the Internet is relevant to those markets. Google generates so much revenue from its online advertising business that it's able to subsidize its campaigns to enter new territory. So when it invades, it may be able to offer prices, services, or synergies that competitors cannot match, at least not without abandoning their legacy business models.

And Google is invading across a broad front--at least that's the way you see it if you've competing with Google. Consumers have largely welcomed their new Googly overlord because, let's face it, free services that work well are pretty appealing.

But online businesses have reason to be wary: Google's mission is "to organize the world's information and make it universally accessible and useful" and that mission continues to lead Google into territory that other Internet companies thought they owned.

Here are 9 markets where Google seeks dominion, or at least a significant cut of the action.