From silverlight.live.com:

While the product is in pre-release, storage and delivery is free up to 4 GB, with outbound streaming up to DVD quality (700 Kbps). As we move out of Beta, developers/designers will have continued use of the service with up to 1 million minutes of free video streaming at 700 Kpbs per site per month. Unlimited streaming will also be available for free with advertising, or with payment of a nominal fee for the service for use without advertising.

If I can get 1 million minutes at 700kps, can I get 2 million minutes at 350kbps, or is it 1 million minutes at up to 700kbps? How will it be measured?

Is this available globally?

And more ‘small print’ – you can only have a 4.3 min video at 700kps.

If the Silverlight application contains a video, the video file must be smaller than 22 MB.
This is equivalent to a continuous video stream of 10 minutes at 300 Kbps. If the video stream is encoded at any higher bitrate, it will have to be shorter than 10 minutes.
For example, if the video stream is encoded at the highest allowed bitrate of 700 Kbps, the maximum length of the video is just below 4.3 minutes.

Free is still good though.