I'll inline my other comment: Mass gatherings of any kind are a public safety issue, and an organized nation-wide protest with anarchist overtones is hardly the least likely to result in violence and property damage. For police to not gather and share information on what to expect would be stupid.
You may get tons of warm fuzzies thinking about OWS, but it still involved thousands of angry people gathering in one place, which is not something any reasonable person expects the police to be wholly ignorant of.
See Also: http://en.wikipedia.org/wiki/Occupy_Oakland#Protestor_conduc...