I got a ticket through the post a while ago from the company monitoring Tesco's carpark in Stafford. I got it because I'm the registered keeper - but it was the missus that parked it. The ticket actually showed that she'd parked and overstayed her welcome twice. They'd ignored the first one and stung on the second. Seems reasonable to me. She would go to town with the kids during the day and park 2 hours in Tesco and then move it to Asda and spend another 2hrs in town, so play the system. Got caught. Fair cop really...
Usually the reason for people leaving their cars in the supermarket car parks is because it's free, and conveniently located to something more exctiing - town centre in our case. I can understand Tesco wanting to discourage people abusing the car park otherwise they end up being dumping grounds for the motors of people working in the town centre and genuine customers wouldn't be able to park on the vast expanse of real estate they didn't build on. The problem lies more with the council not providing sutiable parking at a reasonable cost (ie free) near locations that people want to be. It's signposted, the cameras are reasonably obvious, although personally if they want to employ that tactic I'd make them really, really obvious (or put hi-vis dummy cameras that the local yobs can abuse whilst maintaining the slightly less obvious originals)
I paid the fine and shouted at the missus. It's business, and they're protecting it from inconsiderate motorists. The systems cheaper to run that employing someone to sit and check receipts (and is less of an inconvenience to customers). Just makes business sense.
Yes there's a bit of a moral issue with the data, and how long it's kept for and who gets to see it. Personally I don't think it's a huge infringement on my freedom, but (as far as I know) I've nothing to hide so don't feel particularly threatened or 'watched'. I'd almost considerate it a worthwhile tool for the police to be able to hook into the systems to be able to track criminal movements.
Just my 2p...