I can fully relate to that one wjphoto. Worst part is that when you say anything to these same idiots, they get on the defensive and make daft insinuations that you're down with the police or security or whatever. Spot etiquette should be browbeaten into every kid from the first day they pick up a board. I can't stand going to a spot to see dudes smashing bottles, littering, abusing passers-by and being all-round wankshafts purely because it's not their front room. Worse yet is going to a foreign country and seeing visiting skaters act like every other gobshite on piss-up holidays to Ibiza/Benidorm/etc. abusing locals, being general cunts and the like and thinking they can get away with it because they're on holidays and they're skaters - one time I heard one dude shout back at some local "What are you going to do about it? We're skaters..." WTF??? Shit like that fucks it all up for everyone when local people equate skaters, foreign or local, with everything that's wrong in their city.
Getting back to the matter at hand, it is a hard one, it really does come down to what city you're talking about too - there's a few sites I've seen divulging spots in Paris, Berlin, etc. Both are pretty chilled in regards to skating, but neither have the saturation of spots, favourable climate or cheap cost of living that Barcelona has. Fair enough if the spots on such websites are the main skate all day spots which you get a lot in Europe anyway, but I'd take that as just a starting point when visiting to go out and see what else I can find. Slap published a spot map for SF in 96, which came in handy for me the following year, but I can't say if that had a bad effect on the SF locals at the time. Granted, a lot of problems with spots getting overrun are down to regular kids and the wannabe fake gangstaz who think they're better than everybody when it comes to posting footage of fights with security or just using your brain before skating certain spots like offices or apartment plazas.