For example, if you want to demonstrate the capabilities/contents of a Linux distro, Knoppix and other on-CD versions come in handy because you don't need to install the system, or otherwise change someone elses' system setup or hard disk contents. Just be sure to remind them frequently that it's running slower than would otherwise the case because it must decompress files on the fly.
However, Knoppix can be installed to one or more partitions formatted for Linux, in which it will run faster.
It also wouldn't hurt to keep reminding anyone you demonstrate Knoppix to, of it's value as a rescue CD. Or, for the more patient users, remind them that they can have and use a Linux distro without changing their system (ie, partitioning, installing, etc.), just by running from the CD.
PS: a copy of the Knoppix cheat-sheet wouldn't hurt either.