> I would be willing to bet that you'd be very hard pressed to prove that the majority of the reports in a system like this actually contain factual information

In the US, where I live, you can make legally make reputation-damaging accusations without proving them to be true. Only in cases where the accusations can be proven false is making such an accusation illegal. Personally I think that's a fine system and would be sufficient to keep people mostly honest when reporting others using this app. There is not a whole lot of reason to use a traffic app to try and harm someone when so many more direct means are available.

> The DMV will provide that information to the insurance company after any fines are paid or court decisions are rendered but they are not the legal authority.

Then I imagine they will just discard the reports, and no harm has been done.

> What's to stop your ex girlfriend and her six friends from each reporting you over the course of a month or two for traffic violations to screw with you?

What to stop them from scratching your car just to screw with you? People can hurt you and there is nothing you can do about it. Fortunately they choose not to most of the time.

> Absolutely not, the employer has advertised that they want to know about bad driving by placing the sticker on the vehicle and the employee has accepted that as part of their employment.

I meant when there is no such sticker. Even if the desire to know was not advertised, I believe it would be morally fine to report bad driving of a company vehicle to the entity liable for loss associated with the vehicle. As for the rest of your response, even though you pointed out a number of technical distinctions, I do not see a moral one.

> seems to fit the description of vigilantism . . .

Still no. Vigilante activity is by definition illegal, and this behavior is not.