It's hard to be one of the top tech companies in the world and not run into legal trouble every now and then. For example, Google (News - Alert) is now facing an antitrust probe by the U.S. Federal Trade Commission, which aims to discover if the company is using its leadership in the online display-advertising market to curtail competition illegally, according to Bloomberg.

This investigation comes only months after the FTC (News - Alert) decided not to take action against Google after reviewing the company's search business. Google also made moves to end an EU antitrust probe in April, making several concessions in order to avoid paying heavy fines.

The FTC's latest investigation, still in its preliminary stages, should determine whether Google is using its position in the $17.7 billion U.S. display ad industry to push companies into using its services — an illegal practice under antitrust laws. Google stock fell nearly 1 percent after the news of the probe went public.

The prior U.S. probe closed in January after 20 months of investigation as to whether Google unfairly skews its search results. The search giant managed to avoid a costly legal battle with U.S. regulators by making changes to its business practices and settling allegations that it misused patents to curb competitors in the smartphone market. Specifically, Google said it would remove restrictions placed on its online search-advertising platform, offering companies the option to keep their content out of Google's search results.

This resolution was reportedly not an optimal one for Google's competitors, including Microsoft and Expedia (News - Alert), who tried to convince the FTC to move on to a lawsuit. They claimed that Google's search dominance and its tendency to favor its own services violates antitrust laws.

This is largely what the FTC's new probe comes down to: whether or not Google is using its tools to make companies bypass competing products in lieu of Google products and services, namely its marketplace for busing and selling Internet display ads.