[ninkendo]

Traces are the kind of thing that should be automated anyway... You shouldn't have to write explicit trace statements in your source code, instead your language or framework should have an automated way of inserting these statements at function boundaries. Or even better, attach a debugger and reproduce the issue yourself on the prod server.

Just plain "debug log statements" I have yet to hear a good use case for. Every time people have put them in, it's because some bug called for their inclusion, then the bug got fixed, then the statements got left around after the bug was fixed. Or the bug didn't get fixed and it's a matter of "why don't you fix the bug?"

There's rare cases where there's an ongoing issue with a known bug that you don't know the fix for yet, so you drop debug statements in production code hoping to catch it. But this is supposed to be a rare, rare case.