When Anonymous hacked the intelligence agency Stratfor, it was learned that corporations etc. keep files on activists, and more, beyond simple police worries and DHS fusion center fears.
In Los Angeles, there is a Special Order 1 which makes LAPD a tentacle for the DHS. They even have pamphlets and cards featuring the phrase, "See something, say something". Any records cops have of activists, and because of DHS following Occupy from day 1, you can bet they have them, are loaded up into Federal levels. One person in NYC IIRC while being brought into jail after an Occupy arrest, saw briefly a board in the police station with pics of Occupiers, cross-referencing, etc. Doubtless this exists electronically. \\
http://stoplapdspying.org/
Lt. Paulson, who has been present at or organizing some LAPD assaults upon Occupy LA, is responsible for Special Order 1 as well. Things begin to tie together...
Add in facial recognition and you'll know that if you've been active in activism over the last year, you're in a system on a list, or several. The FBI have broken into apartments searching for "literature", etc. The FBI is after Occupy, among other organizations. Same old tricks they've pulled against civil and social movements for years.
When some SoCal Occupations, Code Pink, and Veterans marched against Raytheon and a few other military-industrial complex war profiteers, there were even at least one watcher on a building rooftop, and -several- who took video from both a distance and while driving right up on the group. They are collecting data and it would be a damn good idea to keep yourself anonymous while protesting. Video (by 5 minutes you'll have the idea)