Based on the title of the article I was expecting the stores to passively collect data based on the MAC address. I guess I was way wrong. I am a traffic engineer and we use passive BT MAC address scanners to sort out origin/destination and travel time. This is done by setting up multiple detectors around a study area. Each detector saves the time and MAC address of every device it detects. We later match the MAC addresses that have been detected at multiple locations and that gives us the travel time between them. The raw data is rather useless for any other purpose, to us at least, and is tossed after we are confident in the data results. If a store were to use something like this, they would have to tie my MAC address to me, which I doubt would be too hard.

I don't see anything wrong with passively tracking people in a store, mall, shopping center, etc., as long as it is used to inform the owners of movement patterns in the area. To use the information to push notifications and determine purchasing habits of people is over the line.