CNN - Social networking site Twitter apologized for a worldwide outage Thursday that left the site inaccessible for more than an hour. It blamed the outage on a technical fault and said that despite speculation, it wasn't related to the London Olympics, which open Friday.

"We are sorry," Twitter's vice president of engineering, Mazan Rawashdeh, wrote in a blog post Thursday night. "Many of you came to Twitter earlier today expecting, well, Twitter. Instead, between around 8:20 a.m. and 9:00 a.m. PT, users around the world got zilch from us. By about 10:25 a.m. PT, people who came to Twitter finally got what they expected: Twitter."

He blamed the outage on the concurrent failure of two data centers. When one fails, a parallel system is designed to take over - but in this case, the second system also failed, he said.

Some Twitter users speculated heavy traffic from the upcoming Olympics was to blame, but Rawashdeh said the cause was simply an "infrastructural double-whammy."

Users of the site joked that they couldn't complain on Twitter that Twitter was down. Others said they were forced to tweet on Facebook.

"When Twitter goes down you'd think I would get more done. Turns out I just keep checking if it is back up again," wrote David Smith of Washington.

Tweeted Jason Carlin of Toronto: "Took time during the Twitter outage to explore some self-improvement. I've written two novels, learned Esperanto, and knitted a sweater."

And from satirist Andy Borowitz: "You learn a lot when Twitter is down. For example, my wife left me four years ago."