I've been occasionally hitting frustrating issues with bash history getting lost after a crash. Then I found this great blog post about keeping bash history in sync on disk and between multiple terminals.
tl;dr is to use "shopt -s histappend" and PROMPT_COMMAND="${PROMPT_COMMAND};history -a"
The first is usually default, and results in sane behavior when you have multiple bash sessions at the same time. Now the second one ("history -a") is really useful to flush the history to disk in case of crashes.
I'm happy to announce that both are now default in Gentoo! Please see bug #517342 for reference.