Travel Technology - WiFi-enabled Apple TV

Apple is now shipping their Apple TV, a set-top box that allows users to wirelessly play their content from the PCs or Macs using a WiFi network ($299 at the Apple store.) Question - is it intended that one will be able to play run-of-the-mill streaming video downloaded on the Internet on the "Apple TV"?

It isn't Apples intentions to allow playback of non itunes / quicktime exports. Enthusiasts are making great progress on that subject though.

Apple is now shipping their Apple TV, a set-top box that allows users to wirelessly play their content from the PCs or Macs using a WiFi network ($299 at the Apple store.) Question - is it intended that one will be able to play run-of-the-mill streaming video downloaded on the Internet on the "Apple TV"?

Its certainly not Apple's intention that one can stream content (other than from iTunes). In fact, recent reports are that they are locking out devices/account of people who hack the aTV.. but I'm not sure how credible those reports are.
That being said, it does appear to be a VERY hackable device and it will be a matter of days or weeks before theres a point-and-click hack that enables things like youtube, bittorrent, divx, etc... and I'm guessing Apple will turn a blind eye... Clearly their intention is to become a content provider, the aTV might even be a loss-leader, at least they want you to buy the content from them..but if you buy 75% and download 25% they still win...

Nevertheless, to directly answer your question, no I dont think apple intends one to stream content that is not provided by iTunes.

divx was added almost immediately (just add a divx codec).

however, this looks even more interesting:

"We all knew it was just a matter of time until someone figured out how to run a full blown version of OS X on an Apple TV, but who'd a guessed it would only take eight days."

http://www.engadget.com/2007/03/31/apple-tv-running-full-version-of-os-x/