Some countries are already doing this, for example Vietnam and China.
I recall reading about it years ago because some enterprising individuals decided that the revenue from catching random violations in-the-wild wasn't enough, so they started to deliberately create dangerous situations, where breaking a traffic law (which would then be recorded and submitted for a reward) was the only safe option for the victim. Unfortunately I haven't been able to quickly find a source to back this up.
This is why optimal policy design has the fines get paid directly from the violator to the reporter. That brings its own quirks, but they're all surprisingly tractable with other market mechanisms.
There's a whole literature on this topic in economics under mechanism design. They've been a longstanding research interest of mine, I consider it almost like the land value tax of legal enforcement by this point.
>This is why optimal policy design has the fines get paid directly from the violator to the reporter.
Absolutely. And make sure to give the violator full contact details for the person(s) who reported them. Better yet, set up sites in isolated areas for the violators to "pay" the reporters.
What could go wrong?