MOUNTAIN VIEW -- An unexplained outage affected countless users of Google's (GOOG) popular Gmail service for more than an hour Friday, while also disrupting the Google Plus social network and some of the company's other Web services, including Google Calendar, Google Docs and Google Talk.

Google offered no explanation for the rare outage, which was a nuisance for many individuals and businesses that rely on the company's Web-based email and other services. Many users turned to social media to make light of the interruption.

"Gmail is down. World productivity is slowly grinding to a halt," quipped Aaron Levie, CEO of cloud storage startup Box, in a post on Twitter.

"Had to walk across my office to talk to someone earlier. Thanks a lot, @gmail" groused Carter Pearson, another Twitter user.

The outage started shortly after 11 a.m. PST; a company statement said that "most of the issues" had been resolved a little more than an hour later.

While no serious fallout was reported, analysts say Google has a lot riding on maintaining Gmail's reliability. What started as a free consumer service is now one of several Web-based programs that Google sells to large corporations and government agencies.

Gmail is more popular than rival services, according to the ComScore research firm, which reported Gmail had 366 million desktop computer visitors worldwide in December, compared with 273 million for Yahoo (YHOO) Mail and 242 million for Microsoft's Outlook.com.

Yahoo suffered a similar, but much longer, outage last month. It can happen to any company, noted Ted Schadler, an analyst at Forrester research firm. But he added, "When a provider of the size and scale and economic importance of Google goes down, and everybody takes a hit at the same time, then a big chunk of the economy stops."

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