One-tap simple.

FaceTime works right out of the box — no need to set up a special account or screen name. And using FaceTime is as easy as it gets. Let’s say you want to start a video call with your best friend. Just find her entry in your Contacts and tap the FaceTime button. Or maybe you’re already on a voice call with her and you want to switch to video. Just tap the FaceTime button on the Phone screen. Either way, an invitation pops up on her iPhone 4 screen asking if she wants to join you. When she accepts, the video call begins. It’s all perfectly seamless. And it works in both portrait and landscape modes.

This is going to change everything. I can't wait to be able to do video calls with my parents, with Kate, with friends all over the world. iChat failed here because it was software. FaceTime will work because it doesn't change the device you use or your existing behavior.

But lets deconstruct the software side of this for a second. Any phone can add a front facing camera, and any phone can add a Skype like application that does video phone calls. But how did Apple make it work out of the box, without accounts?

FaceTime currently works over WiFi only, yet it must use the AT&T network to initiate the connection. How else can my phone find and connect to my mom's phone 500 miles away, using nothing but her phone number?

Leave it to Apple to go the extra mile. Any other company would have made you sign up for something new. But Apple focused on making the software great, and even had to do some custom integration with AT&T. That's what will make it a break out feature, not just something for geeks. My mom and I will do a video call the first day we both have new phones.

At Posterous, we've always believed in avoiding account creation as much as possible. You can post without an account, and you can subscribe without an account. Accounts get in the way. Apple feels the same.

So how does FaceTime work? I guess we'll learn more tomorrow, but it seems something like:

1. Initiating iPhone contacts receiving iPhone using standard telephone protocol (using AT&T).
2. iPhones communicate to determine if both support FaceTime and both are on WiFi.
3. iPhones then create a direct peer to peer connection over the internet. The iPhones deal with all IP addresses, firewalls, NAT issues automatically.
4. Participants can now do a video call over WiFi without use of the cellular network.

But users don't know this is happening. It just works. And that's what makes this technology truly amazing.

Kudos to Apple for making FaceTime an open standard. Skype, you suck. Hopefully we'll see FaceTime added to other devices and networks and it becomes the standard for video chat.