Apple sold more than 600,000 iPhone 4 units in the first day of sales, a new record.

Apple

• The week's best of the internet
• Why Google Glass' privacy concerns are grossly overstated
• Can you buy cool? Yahoo reportedly looking to purchase Tumblr

ritics of exclusive iPhone carrier AT&T have new reason to gripe after Tuesday's pre-order sales of Apple's iPhone 4 turned into a "total disaster." Glitches in AT&T's website burped up error messages and steered some online customers into strangers' accounts, exposing private user data, which some say could result in identity theft. The site's failure also meant long lines at AT&T stores. What caused AT&T's system to buckle? And should customers still be concerned about their privacy? (Watch one fan's description of the "chaos" of the iPhone 4's preorder launch.) Here, a quick guide:

What kind of private information did this glitch expose?
While AT&T spokesman Mark Siegal insists that "the information displayed did not include call-detail records, Social Security numbers or credit card information," Gizmodo reports that "addresses, phone calls, and bills, along with the rest of private information" was exposed.

How did the tech blogs respond?
Mockingly. PC World noted that AT&T was forced to take iPhone orders by pen and paper in a "sad and mortifying" way. Gizmodo, labeling the incident an "Iphonepocalypse," offered this "translation" of AT&T's official explanation: "Our computer systems are a total mess and we didn't really plan for the demand surge."

Why did the problem occur?
AT&T says they were "unable to replicate the issue," and refused to comment further. But according to an anonymous "Apple insider," an update to AT&T's internal ordering system, which they implemented over the weekend, may have been the culprit.

Did the errors hurt iPhone 4 sales?
Not much. Less than 24 hours after iPhone 4 pre-orders began, Apple's next generation smartphone is completely sold out. The Apple Online Store is still taking pre-orders, but new customers won't receive their device until July 2. "The fact that Apple blew through their entire first run of iPhone 4s in something like 20 hours is impressive any way you slice it," says MG Siegler in TechCrunch. "But it also begs the question: how fast would the device have sold out if the pre-order system actually worked"?

Sources: Gizmodo, NY Times, TechCrunch (2), Boy Genius Report, C.S. Monitor