Last week, after nearly two years of waiting, Google Voice finally enabled number porting — the highly requested feature that lets you transfer an existing phone number to Google's powerful telephony service. And then, just as everyone was getting excited, the feature disappeared. But now it's back. Turns out last week's number porting launch was just a test (which is why Google didn't announce it). Given the logistical hurdles involved it's not really surprising that Google wanted to kick the tires first, and now it looks like they're pleased with the results. Google Voice number porting is going live today for all existing accounts, and new accounts will be able to use number porting in the next few weeks.