Google Inc. (NASDAQ: GOOG)'s will report its second quarter earnings today after the market close. The search engine company will most likely meet or top hyped estimates once again. Literally, Google is becoming an unstoppable force in internet advertising. With more traditional media dollars flowing to the web and away from radio and print mediums, Google stands to grow ever taller.

In June, that sentiment was proven once again as Google's U.S. internet search market share neared 70%. We're talking 69.17% of all searches performed in the U.S. -- home and business -- belonging to Google and its various tentacles. The competition lost market share as Google gained it. Although the gains and drops were small, it's all relative. A 1% drop or gain can mean tens of millions of web searches (or more).

It's taken Google about two years to come from the 60% U.S. search market share level to near 70%, as it crossed the 60% level in July 2006. The company has only grown stronger since then, and Google's advertising inventory increases as its search engine is used -- and that's how Google makes almost all of its money. It can continue to grow its revenues if it continues taking search market share. If that slows down, Google will need to step up the monetization of its other products pretty swiftly. Therein lies the Achilles' Heel for GOOG investors.

Google, Inc. (NASDAQ: GOOG)'s market share in April increased once again, going from 67.25% to 67.90% of all internet searches performed in the U.S. Sounds like a tiny increase, but we're talking hundreds of millions of additional searches here. Even a tenth of 1% is a major increase.

Google also earned the distinction today of being named the No. 1 most-visited site by ComScore, topping Yahoo for the first time.

Both Microsoft Corp. (NASDAQ: MSFT) and Yahoo, Inc. (NASDAQ: YHOO) saw decreases in search market share due to Google's continued dominance. April data from internet traffic research firm Hitwise indicated that Google continues to dominate U.S. internet searches, while being responsible for the lion's share of connecting web searchers with specific industries as well.

For example, 31% of of web traffic and health and medical sites was supplied by Google, as well as 23% of web traffic to travel websites. This alone demonstrates the power Google has over the web. Some industries would see huge decreases in traffic if Google were to go away. In effect, Google's web search dominance has a very broad and meaningful over entire industries on the web, including shopping and classifieds, news and media, entertainment and others.

Still think Google is worth $576.30 per share?