“If the parties cannot agree, it will be left to the competition-law agencies to grapple with the difficult issues of how patents are priced,” said Mr. Carrier, who is the recipient of a Google Research Award but who does not consult for any of the companies involved.

Mr. Carrier said that a single smartphone was built using hundreds of patents, and that the owner of any single one of those patents could hold up the entire industry, helping fuel a vicious cycle in which technology companies were being “forced to spend money to build an army of patents” to fend off litigation.

A prominent commentator on the issue, Florian Mueller, who also advises companies including Microsoft on patent issues, said that Google and Motorola would probably need to defend themselves vigorously to avoid being sent formal charges in this case.

“Google should think hard about whether it wants to get a 100- or 150-page statement of objections at some point relating to standard-essential patents,” said Mr. Mueller, referring to the document E.U. antitrust regulators often send to companies under formal investigation.

Mr. Mueller said that Motorola Mobility had shown “aggressive litigation and enforcement activities in Germany” and that if “every owner of standard-essential patents behaved like Motorola, this industry would be in chaos, and grind to a halt.”

The U.S. and European authorities have cleared the Google-Motorola deal, but Google still is waiting on approvals from China and other parts of the world.

In his blog post, Mr. Heiner said Motorola was unfairly trying to block Microsoft and other companies from using technology that devices needed for functions like connecting wirelessly to the Internet and playing video. Mr. Heiner complained that Motorola had refused to make patents available at “anything remotely close to a reasonable price” and had demanded that Microsoft remove Internet and video functions, or take products off the market.