AT&T's for the iPhone all include "unlimited data" -- that is, unlimited Internet usage. But only the premium US$130/month Unlimited plan allows iPhone users to make all the phone calls they want for a fixed price.
Skype for iPhone means anyone willing to figure out the app could potentially order AT&T's entry-level $70-per-month plan, then use Skype and Wi-Fi connections to make as many calls as they want to over the Internet, potentially cutting their monthly payments to AT&T in half (the AT&T Nation plan costs $130 per month for unlimited U.S. calls).
But Skype for iPhone will require an available Wi-Fi connection, which severely restricts its availability to users on the go, compared to making calls over AT&T and other carriers' 3G and EDGE networks.
Skype, an Internet telephone service launched in 2003 and acquired by eBay in 2005 for an eye-popping $2.6 billion, is popular among tech workers, students and others willing to deal with setup and configuration issues. Like any phone service provider, Skype has been criticized for . But users willing to tinker a bit are able to make free calls to other Skype users. They can call non-Skype phones in the U.S., Europe, China and most of the world for about , or buy for as low as $3 per month.
But adding a Skype app to the iPhone means even non-technical users can figure out how to get unlimited calling much cheaper than AT&T's price. New customers can always start with the lowest price plan and, if they're not happy with Skype, upgrade.
When the iPhone debuted in June 2007, Apple restricted application support to only those that Apple and AT&T had determined were not likely to overload AT&T's digital networks. Now, two years later, AT&T has agreed to allow Skype for iPhone onto its networks, potentially giving up millions and millions in phone-plan income.
The company has managed to control gossip about the decision. But you have to wonder: Did AT&T reluctantly forego a big chunk of revenue, or is this an eager plan to lure new phone buyers away from cheaper models by offering them an iPhone with unlimited calls for under $80 per month in AT&T and Skype fees?
Update: As noted by a reader, Skype's restriction to Wi-Fi rather than 3G or EDGE wireless networks limits Skype's availability to mobile users. The Wi-Fi requirement was referenced in an earlier version of this post, but the Standard has clarified the 3G/EDGE issue.