[developer2]

1. Regarding commands with credentials or sensitive info, bash allows you to prefix the command with a space character to omit saving the command to the history. This requires remembering this fact, and of course you get nothing in your history to refer to later.

2. I remember a HN submission for a piece of software (or collection of softwares?) that provided a centralized log of your command history across multiple machines. In this way, if you are working on multiple machines in a cluster, you can later search back through your histories from those machines in a single location. My Google Fu is failing me now though.