Rumor has it this led to more than one divorce and the municipality has since changed the way they store the license plates and will likely not take part in the distribution of such sensitive data again. (At least, not voluntarily.)
The incident did wonders for people realizing that they too valued privacy.
Just kidding, because you really have nothing to hide. But not everybody is like you. Plenty of people go about their business not realizing that they're being followed all the time. They think they can get away with whatever it is they are doing because they are making (flawed) assumptions. And not all of those are bad. What about someone important undergoing medical treatment? Would that influence the stock of the company they are leading? What about a person visiting an AA meeting? What about someone having an abortion?
All these things affect your private life in a very immediate and drastic manner and in some cases they'll affect the rest of the world as well.
Databases like these shouldn't even exist.
I'm normally in favor of public data being public, but in this specific case I think the potential for abuse (and the ease and extremity of that abuse) might outweigh the benefits of being this free and open about this particular data set.
That said, even with randomly generated unique tokens, I suspect knowing where someone was at two or three specific times would be enough to deanonymize them.
You could find where someone lives based on an instagram photo of them standing behind their car.
You see a car in a driveway and check it against the app you built with this data to find out when they're not home to interrupt your burglary.
You could plan hijackings of valuable shipments.
or kidnappings of wealthy people.
Lots of crap you can do when you basically know where someone or some vehicle is at all times.
I'm sure there's much worse, that's all I can think up from comic books and TV, but real pro criminals must have a million uses.
Health insurance companies could raise your rates if they see you parked near McDonalds. Retail chains could use the data about your traveling habits to enhance their habit tracking of you. etc etc etc
It would be straightforward to demonstrate that your rates had been increased compared with others in a similar bracket within your area. This would have significant legal repercussions for the insurer that they would be incentivized to avoid.
If you have someone's license plate you can get their registered address through online services (I've used docusearch). We're all driving around like jerks with our addresses printed on the back of our cars. It's really silly.
I'm having a harder time thinking of how an entity with sufficient funds wouldn't be able to misuse this.
If you're a declared "non-smoker", and die, and there's a picture of you taken after your policy data of you smoking a cigar, weed, or cigarette... good luck to your family's collection efforts.
Many health insurers are collecting lots of trivial under the new "wellness" programs that are popping up. You can be sure that they are trying to correlate gym attendance vs. various claim events.
I believe Ars was able to accurately track an Oakland city councilman using similar data. 
Is that a euphemism for "illegal"? If it is, let's all agree to call a cigar a cigar and stop unwittingly assisting the spin machines of criminals and/or authoritarians. :)
It's better to use a construction similar to the following:
"I'm not a lawyer -so I might be wrong-, but according to 123.e.(g).1 of $LAW, it looks like $THING is illegal.".
Authoritarians and other folks in power love to downplay the seriousness of their actions with soft talk and babytalk.  It's better to be explicit about your uncertainty and potential lack of qualifications to interpret source material, rather than to simultaneously imply your lack of expertise and reduce the perceived seriousness of a prohibited action. :)
 Please note that this is not a criticism of you. I try hard to say only what I intend to say and leave nothing to interpretation.
now the question I have, are there other accessible data bases from which you can tie these back to their owners?
But then it's not even anonymous, so I could just look my neighbor up by their license plate. What about jealous partners? What about thieves that instantly know everyone's work patterns? What about your boss seeing if you actually did stay home sick that one time?
These sort of "emergent" privacy leaks are interesting. Information that is already "out there" but being collected and distributed for the first time is like a system shock when it happens.
Chicago Tribune pretty much did this after a FOIA request for red light data was published. It's not searchable by owner name, but it's still pretty terrible.
I've sent many FOIA requests for parking ticket and towing data - the license data gets redacted every single time. I'm really curious about how the tribune got that data. FOIA specifically forbids license plate information from being released.