Google bought 48 companies during 2010, a buying spree that cost the Internet giant $1.8 billion, and a pace of acquisitions the company said it plans to continue through 2011.

The price Google paid for the companies, their technology and their talent included $681 million for the mobile advertising technology company AdMob; $179 million for social technology company Slide; $158 million for Widevine Technologies, a content protection and video optimization company; and $123 million for On2, a developer of video compression technology. The price tags of those companies, plus an additional 44 acquisitions totaling $669 million, were disclosed in Google’s 10-K form recently filed with the Securities and Exchange Commission.

Google’s acquisitions price tag did not include the largest purchase it announced in 2010 — its proposed $700 million purchase of travel search company ITA Software, a deal that is being scrutinized by federal antitrust regulators.

“Acquisitions are an important element of our overall corporate strategy and use of capital, and we expect our current pace of acquisitions to continue,” the company reported in the filing. “These transactions could be material to our financial condition and results of operations.”

Some parts of Google, particularly research and development, grew more quickly than other areas of the company. Google said in the filing that its buying binge helped fuel a 28 percent jump in the number of Google employees working on research and development, double the 14 percent growth in R&D head count during the previous year. R&D spending grew by $919 million, compared with $50 million in the previous year.

Google declined to comment beyond what it disclosed in the 10-K filing. The company’s total work force grew by 23 percent in 2010 as it added 4,565 employees, bringing its global work force to 24,400. The number of employees working in sales and marketing grew by 20 percent, while the number of Googlers in general and administrative functions was up 14 percent. Google did not disclose the total number of workers it has in those areas of the company.

Google also provided more detail in the filing about how it valued the largest companies it bought in 2010.

Google recorded about 85 percent of the purchase price of AdMob and Slide as “goodwill,” an accounting term that reflects management’s opinion of a company’s future value and prospects beyond the assets listed on its balance sheet. Widevine Technologies, which Google bought in December, had a larger share of its value in patents and developed technology, but still assigned 60 percent of its value to goodwill.

“Technology companies are all about people; they are all about ideas — stuff that accountants, for better or worse, don’t put on the balance sheet,” said John Percival, a professor of finance at the Wharton School of Business. “But when you buy a tech company, that’s really what you’re buying.”

The large share of those purchases recorded as goodwill “is not necessarily a bad sign that anything evil is going on here,” Percival said. “It represents a company that has been really aggressive in acquiring businesses that didn’t have a lot on the balance sheet in tangible assets, but where management feels, in their opinion, there are bright future prospects for those businesses.”

Contact Mike Swift at 408-271-3648. Follow him at Twitter.com/swiftstories.