AC10 said:
If it wasn't provocateurs, then it's at least a self fulfilling prophecy. Members of the Black Bloc stated they wanted to test the security and show the government they couldn't contain the people like that. If they government didn't they probably wouldn't have been there. Or, you could argue they would just find some other thing to get violent about.
People will find an excuse to do as they like when they like. Rationalizing it in their own minds to twist reality to their own perverted whims. There is absolutely no doubt whatsoever in my mind that that group would have caused untold trouble no matter the situation. Had there not been as much spent, then they'd say they were protesting how ineffective the precautions were. Had a bloody boat-load been spent, then they'd protest there having been so much spent on precautions.
It's human nature, you know that!
That said I'd rather money be spent on safety than not. As you point out, there are tens of thousands of other people involved whether they like it or not in the protests, not all are violent, but all have the possibility of being drawn into violence. Plus it is a city, a living breathing place where people live and work we're talking about here. Would you rather them have done nothing and let the riots escalate till there'd been more damage done and the costs of the repairs went into the billions itself? We're already seeing footage of vehicles burning and building fronts being wrecked.
Not to mention the obvious threats of Mob Mentality. All it takes are a few people to spark something worse. Better the Police are given the tools to end it quickly rather than risk things that!
I see nothing wrong with the precautions taken. It's alot, to be sure, but this is the homes, workplaces, and lives of people at stake. No cost is too high!
Of course logically the best course would have been to not host this event in a city at all, but do like they did awhile back with the 28th G8 Summit and just host the thing in the bloody middle of nowhere.