As long as it's in a place where there's no expectation of privacy, it's usually allowed. This is for the property owner to monitor their building which, at face value, isn't really different from monitoring a warehouse, except for people doing things in the back yard that might get out of hand, in a way. If the property has multi-story buildings around it, I think the privacy issue is probably moot. As long as the cameras are set in a way that viewing through windows isn't possible (and some, like Digital Watchdog have a privacy feature), it should be a good thing.