I think these taggings are more premeditated than folks like to think. And knowing they're being watched will only lead to them finding more ways around that. Or tagging more things that are not being watched. And so forth...I doubt vandalism of this sort is premeditated to the point of someone resorting to wearing masks for it.
...it boils down to me of having more security at the expense of our freedoms. We will likely end up with neither.