The simultaneous phone launch in 21 nations -- with large crowds in New York, San Francisco, London, Tokyo and so on -- helped bring Apple's servers to a crawl, with the network going down for several hours during the phone's launch in the United States.  

Apple sold out of the new iPhones in 95 retail stores, with a large number of AT&T stores also selling out.

Apple reportedly sold more than one million iPhone 3Gs worldwide, despite activation problems spread across the world.  It took Apple and AT&T 74 days to sell 1 million original iPhones last year. Apple also reported more than 10 million downloads of iTunes App Store applications.

Learning from mistakes made last year, Apple and AT&T forced users to activate the phone in the store, effectively tying the owner to a phone contract so it could not be later unlocked and used on a different phone network.  Last year's original iPhone launch did not require the in-store activation, adding even further stress to the Apple network.

Many new iPhone owners were sent home with a phone that had to be activated via iTunes, but the number of users activating through iTunes also brought down the network.  Software and network problems in London caused iPhone owners on the O2 phone network to wait in line for several additional hours before being able to head home with their new phones.   The network disaster also affected previous iPhone owners, who tried to update their phone only to be left with bricks as iTunes was overwhelmed.

The iPhone 3G phone activation seems to have righted itself over the weekend, with fewer complaints about Apple network problems.  Furthermore, the lines to get the iPhone 3G at both Apple stores and AT&T satellite stores has quickly diminished, though many smaller stores still do not have the phones available in stock.