Yeah, that's a great idea. How would you get the tape? Security cameras typically broadcast onto a closed-circuit network, which is then taped. In some situations, There can be one tape showing a pint-sized version of each camera, one tape switching between each camera, and then a single tape per camera. In some cases, these tapes aren't even made by the business, but by an outside company, meaning you'd have to track the company down and sneak in to obtain the tapes.
Of course, if you're trying to do this at a gas station or somewhere similar, have fun. Most gas stations around here have a separate camera in the manager's office that feeds either directly to a remote location (the way I just explained), to a hard drive (if the company can afford digital security cams or just uses all x10 stuff), or to another location for security. The gas station down the street from me has the manager's camera feed directly to the manager's house (next door), though this could also be an anomaly.