according to info on the directions on the ubuntu live dvd session, it says that the computer may be compromised by doing this? why would one want to take this chance?
Security and Updating
While linux systems are more secure than Windows, LiveCD sessions are not meant for long-term use nor for sessions lasting several days. Because LiveCDs can't easily be updated, they may well be vulnerable to security issues discovered in the months since their release. They also can't protect you against scams such as phishing. If a criminal broke in to your live session, any changes he made to your session would be reset along with everything else when you reboot, although he could make permanent changes to the computer's hard drive.
A persistent image can be updated as new security issues emerge, but also lets any damage done to your computer persist across sessions.