If you are using ext2 or ext3, you can also change the attributes such that the owner of the file cannot remove or modify its contents:
chattr +a ~jerkhathacker/.bash_history
Only the superuser or a process with the CAP_LINUX_IMMUTABLE capability can clear it.
There's also +i, which disallows even append. This still doesn't protect against unset BASH_HISTORY or the other options where you tell bash to stop logging, though.