Heh, where I live, in Italy, I have sort of the same problem.
I am in a building full of old people.
We have some private parking places, but not numbered.
In 2 years of living here, I got my car's paint scratched five times, and the front glass broken by a BIG stone.
All vandalism, and all done by old people.
I know because my other "old people" neighbours told me that other think that they own the place, and especially the parking places (which are too few for all of us).
So if you park somewhere they don't like, they scratch your car.
I considered a lot of times the sec camera.
The point is, they do it during the night, since there are a lot of people going during the day. so a sec cam... well, won't really work.
At least, I'm insured vs. vandalism.
but it still costs me 100-150 € as franchise everytime.
So right now, I'm keeping the last three scratches to my car. One day, I'll repair it, again.
If someday I find a way to get a cheap sec cam that can watch during the night, then I will buy it and install it.
Then, I will put the car in a precise place where I legally can park but where I know it will get scratched, and I will wait.
When I'll find out the guy that do this, I won't tell him anything.
I'll wait some 6 months, and then wrack his car, life, everything tenfold.
No pity for vandalism.