Complete dweeb question.
When signing up for FF Programs, they ask you which other programs you are in.
Should you reveal ? I lean towards no.
What do others think ?
Personal choice obviously.
If I had status with an airline, and was wanting to get a status match in the future with a new FF program I was signing up to, then I would absolutely tell them. How else would they know you are flying/spending $ with a competitor? Obviously you could also email them and ask! 
I don’t fly enough revenue tickets to worry about status, so I usually don’t tell them what programs I am members of.