Because it is in PRIVATE BETA mode, it is not easy signing up for the site. You have to be invited. I was just invited this morning (of this post) and decided to create a mambot for Joomla! featuring Seesmic. Unfortunately, I do not have a video camera at this time or a web camera, but I will demonstrate Seesmic with other user's videos.
Please comment below to show me where you used this plugin with the URL.
All you have to do is copy the videocode and insert it into the mambot code. The width and height would allow the size change.
If you are looking at a video in Seesmic and the URL does not show the right videocode, you may have to copy and paste it from the URL code underneath the video. This is due to the fact that the page does not refresh when viewing multiple videos.