Actually, all of the carriers are pushing for this. As everything goes data (including voice and text), then carriers will be changing their data rates. It's why Verizon and ATT went to metered data plans, and why they are both pushing for shared data plans. The hope is over time you will have to keep increasing your data contract as your family uses more data, and thay most people will not consider (initially) that voice and data are contributing to your rise in data useage. Also they will get you on charging for the data overages.
So adding to the list of disadvantages:
- more out of pocket cost on your data plan.