I once worked for a company that did pre-employment background checks. Before I left the CEO was talking about the next big thing in weeding out undesirables from the workforce: a system that would keep track of every time someone was placed behind bars/arrested, adding that to a database, and notifying potential/present employers that person A either working for them or applying to work for them had been arrested, either at one time or now.
Not charged with a crime, not falsely arrested, just simply placed behind bars. I left before really delving into the legality of it, but it apparently was.
Remember, the bill of rights only applies to the government. A private company doesn't have to care about WHY you were placed in a jail cell or whether you actually are a criminal, just that you were detained by the police at one time.
If every protester who'd been arrested (I'm thinking Occupy from a while ago) was now in a database that prevented them from ever getting a job again even though they've never committed a "real" crime, then being legal sure doesn't seem fine at all.
I should also mention that I've worked for a few companies handling private information about people. The lack of security in the private area is astounding. I'm honestly surprised that massive SSN and other personal info don't leak out of private companies more often, most of the time it's not difficult to walk out with a million DOB/Name/Current Address/SSN/Duplicatable Signature on thumb drive, there's no internal tracking and no encryption most of the time. The private sector is the last place surveillance should be happening, it's really frightening to think what could happen should they mess up.
Most police forces are institutionally right wing, and so are quite happy to help corporations build blacklists to keep people involved in unions or who brought up health and safety issues out of work. I'm sure police forces hate left wing occupy protesters and will be quite happy to supply detailed information about who they have arrested or information gained from undercover operations to help build blacklists.
Police officers across the country supplied information on workers to a blacklist operation run by Britain's biggest construction companies, the police watchdog has told lawyers representing victims.
The Independent Police Complaints Commission has informed those affected that a Scotland Yard inquiry into police collusion has identified that it is "likely that all special branches were involved in providing information" that kept certain individuals out of work.