Of course not. My position is that if one person is wrongly persecuted despite breaking no laws, they should not be considered a suspect. Once police decide "We need the list of everyone who downloaded the app.", those 50,000 people are all suspects.
Here's what I _would_ be in favor of:
-Police bust Catalyic Converter Kingpin in one form or another
-Police learn in the course of investigation that said kingpin was a prolific user of said app
-Police subpoena the usernames of accounts that corresponded directly with the kingpin
There's a compromise to be had here without throwing 50,000 into a digital suspect bin when maybe half were people actually complicit to...wait for it...a crime.