Facebook's U.S. user numbers started to grow again in June, which is the month that Google launched its rival, well-funded social networking site, Google+.
"Google+ doesn't seem to be putting much of a dent in Facebook at this point," said Olds.
"This doesn't mean that [Google] won't or can't, but it does mean Google is losing precious time in its race to get some mindshare with social network users. While Google has the resources to do about anything it wants, the one thing they can't do is turn back the clock to a time before Facebook was the dominant player in social networks," he added.
Shimmin said it's too early to tell how the new social network will fare.
"From my perspective, Google+ is still undergoing the typical peak-and-valley associated with new offerings," Shimmin said. "I don't think we'll be able to assess the health of this service until it has further matured, entering the enterprise marketplace, for example."
Sharon Machlis and Ken Gagne of Computerworld compiled the data on which this report is based.
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