Video in Flash, Alpha within or extrnal

I’ve been getting an impression from not only macromedia’s official web site, but a few other proects as well that u can use alpha within flash to remove backgrounds and such. I haven’t found a way to do it so I’m asking you:

Can flash do this, or is it all done with other programs and greenscreen?

The only thing that I feel supports this rumor is flash 8’s new webcam interactivity feature.

-KingNuke