Try it next time you're mingling with ops people. Say in a bar at a conference. Don't look at what they answer. Look at how they answer. Some people are comfortable not knowing. Some people are excited to discover the ones they forgot they knew. some people get curious and eager to fill the hole they've just noticed in their knowledge. And some people get defensive and peevish.
Again, this is one of those, "Here's what I've got cached, and here's where I'd look up what I don't know offhand" questions.
From the ps manpage:
Note that "ps -aux" is distinct from "ps aux". The POSIX and UNIX standards require that "ps -aux" print all processes owned by a user named "x", as well as printing all processes that would be selected by the -a option. If the user named "x" does not exist, this ps may interpret the command as "ps aux" instead and print a warning. This behavior is intended to aid in transitioning old scripts and habits. It is fragile, subject to change, and thus should not be relied upon.