There's no proof that they don't either.  It's not as complicated as you'd think.  Considering how many sloppy sellers there are on Facebook.  Yes it won't stop all, but I'm of the mindset that taking even 5 or 6 people out of commission is better than none.  

Did you know unless you call APD or have them come to your home that they can't take a report online unless its specific to their new website? 

How does that make any sense.  You can provide them with evidence but unless you're making a "technical" report then they don't investigate. 

Sadly I know for a fact that people in this town are selling to criminals.  Because I happen to be related to one.  He watches more legal guns hit the street than most because he's a participant.  Between home invasion thefts, and legal guns sold illegally secondhand its no wonder we have the issues we do. 

And no you can't report someone to the police for telling you they commit crimes. I've tried it doesn't work. 3rd party info. Eye roll.