Antitrust authorities in the U.S. and Europe are taking a closer look at Google (Nasdaq: GOOG), and this is not a good thing -- at least not for Google and its shareholders. In recent weeks, news has emerged of two issues that have caught the eye of regulators.

In the U.S., the Federal Trade Commission is gathering additional information in its review of Google's planned acquisition of AdMob, a leading mobile advertising company that would help Google extend its desktop dominance to mobile devices.

In Europe, where Google's 90%+ search market share in countries such as France and Germany makes its U.S. share seem unremarkable, antitrust authorities are looking at the fairness of its search result rankings following complaints from local Internet competitors. Interestingly, one of the complaints is from a subsidiary of Microsoft (Nasdaq: MSFT) -- a company that knows a few things about being investigated for antitrust violations.

These two examples are not the first time Google has raised the eyebrows of authorities. Just last year, antitrust officials thought shared board members made Google and Apple's (Nasdaq: AAPL) relationship too cozy. What a difference a year makes.

While it's too early to know what will result from the latest scrutiny -- other than a big legal bill -- they are bad news for Google. The investigations may push the company into defense mode as growth in its core business slows. Google needs to stake claim to faster growing markets.  

Antitrust regulators have a history of conducting prolonged investigations in the technology industry. Microsoft, IBM (NYSE: IBM), and Intel (Nasdaq: INTC) have all faced seemingly endless investigations. The results of those multiyear investigations: Intel was fined more than $1 billion, and Microsoft agreed to share its application programming interfaces (APIs) with third parties, while IBM incurred no penalties, except for being under investigation for 13 years. The real punishment to the companies -- and their shareholders -- was the inquiries themselves.

During a lengthy investigation, it's easy to imagine a company competing a bit more tentatively, concerned at how an aggressive deal or expansion might look to antitrust authorities. Microsoft, IBM, and Intel have all continued to thrive despite their experiences, but it's hard not to wonder "what if." If Microsoft hadn't spent much of the 1990s under investigation, would it, rather than Google, dominate search? Might Microsoft now have 90% market share in mobile operating systems? As a Google shareholder, I fear similar questions may be asked about the company in a decade.   

Fool contributor, April Taylor, owns shares of both Google and Apple. Intel and Microsoft are Motley Fool Inside Value choices. Google is a Motley Fool Rule Breakers selection. Apple is a Motley Fool Stock Advisor recommendation. The Fool has created a covered strangle position on Intel. Motley Fool Options has recommended a buy calls position on Intel. Motley Fool Options has recommended a diagonal call position on Microsoft. Try any of our Foolish newsletters today, free for 30 days.