Everyone should be concerned about privacy. Mymagic may prompt the concern, but you should look at everyone who tracks you.
YES! ... That is so, so very true.
I think the issue is Disney is dipping its toes in a very big ocean and everyone out there with a product to peddle or service to sell is waiting to see how far Disney can go with this.
WDW has the ultimate controlled atmosphere to execute this with 24/7 access to guests staying in its almost 30,000 hotel rooms, timeshares and camp sites.
They are like the bellweather. If Disney can do datamining on a massive scale and get away with it, then everyone from apparel companies and airlines to automobile manufacturers to etc will be trying to slip and slide the 'Disney Model' onto their businesses.