Why Are People So Excited about Skype 3G?

The availability of Skype for the iPhone on AT&T's 3G network has excited lots of people. But why exactly? Skype has been available as an app over WiFi for quite some time.

My theory is that this is suggestive of potential carrier independence at some future point -- and that's what got people all excited. As a practical matter why would you choose Skype over 3G vs. AT&T's native calling in the US? If the 3G network isn't working then presumably Skype wouldn't either.

The only reason right now to use Skype mobile is for international calling, or potentially for free conference calling. 

In a scenario where one had an unlimited data-only plan (which AT&T just killed) I could imagine using Skype as the voice part of the equation and skipping the carrier's voice plan altogether (or buying the minimum voice plan) to save money. Right now however Skype's quality, though greatly improved, is still not quite competitive with carrier voice. There are some, I know, who disagree with this assertion. 

Regardless, Skype is improving and is increasingly positioned a potential alternative to traditional landline and maybe wireless carrier subscriptions. The barrier to the latter scenario is carrier plans and pricing, as suggested. Right now other than AT&T for the iPad, T-Mobile is the only US carrier that doesn't have a mandatory voice plan along with data plans. 

Eventually, however, we may see more people dump traditional carriers and simply use Skype across landlines and mobile devices for more and more of their voice communication. 

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Update: Skype said that five million iPhone users downloaded the app since Sunday.