I have yet to jailbreak my personal iPod touch but interesting news has come to my ears from a variety of sources. Many iPod touch jailbreakers find that their systems lose read-write access after reboot. The iPod seems to "self heal" and "modify" the /etc/fstab file on their system.
The problem may simply arise from the file not getting written properly during the jailbreak itself. For the moment, iPod touches that are jailbroken using older (primarily Windows) versions of iPhuc are leading this trend while Mac jailbreaks resist the reversion. More as this develops.