- because it makes demonstrations easy, in for example a teaching environment with a PC+projector.
- because it can be used to make "screenshots", of for instance an Add-in you are making. Much easier than using CAPT and then transferring/converting files afterwards.
- because you can.
I made "screenstreamer" which does this as well, but is available for OSs where libusb 1.0 works. This means Linux and Mac OS X, as of july 2009. screenstreamer is open source software.
To get the source code, you need subversion ('svn').To compile and link the sources you will need GCC, make, Qt (for development) and libusb 1.0. They should be easy to get on most Linux distributions.
Once you have that you can follow this video guide for Linux. (I don't use Mac OS X, but if you do and are able to get the program working, I'd love to hear about it.)
or follow written instructions at http://fxsdk.sourcef...=screenstreamer if you don't have flash.
I hope this can be useful, and know there is at least one linux user here

