That was mainly because the speakers did not let us know whether they would require a computer beforehand. It was only when they started to walk towards the microphone would they let their desires be known. Add to that the confusion when someone would want to give a presentation about Free Software and Free Knowledge, which they had made on proprietary applications, on their own machines running MacOS.
<sigh>
i've generally found, that if one buying a Mac and one does not want to use Mac OS X(of which some components of the GUI(Aqua) are under non free licenses), either fry the machine and put a GNU/Linux distribution on it or don't use Aqua, install a Free GUI and the other Free app's with along with Darwin. That's the way to go.
Regards,
- vihan