The service: Web advertising
Its function: Google's core money-maker, a service that places ads on related search results.
The problem: Some advertisers have complained that Google buries the ads of potential competitors, a claim Google strongly rejects. While prominence on the page is partly the result of how much money an advertiser is willing to spend, it is also determined by an algorithm that makes sure the ads are relevant. Google says this process is completely automated.
The risk: Low-medium. While some advertisers have taken their complaints to court, those cases have done little to temper Google's popularity in the world of online advertising, where it continues to make most of its money.
The service: YouTube
Its function: The world's most popular video site, it gets more than a billion views a day.
The problem: Since its inception, YouTube has faced complaints from various copyright holders. Most notably, music- and movie-distribution companies have raised red flags over portions of their content appearing on the site without authorization or payment.
The risk: Low. Google has been quick to take down any videos that result in a copyright claim. It also has brought several big entertainment companies on board, leveraging the site to make money for both parties.
The service: Google Voice
Its function: The company's new, virtually free phone service is supposed to let users link all their phones to a single number, and manage their communications from a central Web hub.
The problem: Rules by which the phone industry currently plays weren't designed for a digital age. Traditional carriers are bound by myriad regulations, which the carriers contend give Google Voice an unfair advantage.
The risk: Medium. Google contends that, since Voice is not a traditional phone service, it shouldn't be bound by traditional phone regulations. Regardless, regulators are keeping a close eye.
The service: Book Search
Its function: Google's attempt to digitize the world's store of books, initially ad-hoc and then through a proposed legal settlement with authors and publishers.
The problem: Critics argue such a plan would give Google a near-monopoly over digital books. Google rejects the claim, saying there's nothing stopping others from attempting to do the same thing.
The risk: High. Google's original proposed settlement with authors and publishers fell apart after the U.S. Justice Department - along with hundreds of other groups - raised concerns. The parties have until Nov. 9 to come up with a revised settlement, but it's not clear what changes will be made, and whether they will be enough to get the project out of its current stall.