The license plate wiki is interesting, but I fear the privacy implications. Sure, it may be legal, but it would still make me uneasy. I can see someone e.g. escaping their abusive spouse only to have their position given away online.
Or people outright lying for revenge. Or bad drivers blaming other people.
Wouldn't the wiki-community-spirit help prevent this kind of thing? Guess not, it'd be one person vs another.
This would only work if people were also incentivized to post good stuff about you; for example on Ebay, even if you have a dick downvoting you unjustly, the amount of good feedback will probably make it up. But here, there's none of that.