We have that in Spain as well now that you mention it, we can use the horn in those cases too.

What's with all these horn laws anyway? I mean what's the purpose? I thought NYC was quite strange for having that but now everyone's saying that their country has them too. In most of the US (with the exception of NYC and maybe a few other large cities I don't know about) you can honk and honk as much as you want and it's perfectly fine and legal.

Here the German, Austrian and Swiss law about horns:
http://de.wikipedia.org/wiki/Hupe

Every car with more than 50 ccm must have one

Only to use for
- warning others for a danger
- outside a village/town to show, that you want to pass

It forbidden and you can be fined, if you use it for:
-wake up a sleeping driver in front of a traffic light
- to indicate annother ones for a misbehaviour
- to chase away bad ghosts at a wedding in the convoi
- greeting friends
- making a horn-concert after your favourite team has won

P.S. The last use of a horn was made popular in Germany by Italian and Turkish immigrants. At the last football-cups in 2006 and 2008 it was used by the fans of all teams.

I am using my horn when it is necessary - I believe, that it is better to be called honking idiot, than to have a smashed car..