WOW thats stupid..... they should give YOU the choice to share or not give people a little freedom in there decision making instead of making them share data their paying for
YOU do have the decision. If YOU do not want to SHARE data with others on a SHARED plan, then don't enter into a SHARED plan with others!
By SHARING a plan with another, though, you are lowering the cost for BOTH of you. I don't see how this is "stupid".
Share plan with 2 smartphones: $80 for phone access (2 x $40) + $70 (4GB of shared data) = $150 ($75/person) + taxes.
Individual Share plan with a smartphone: $40 for phone access + $60 (2GB of shared data) = $100 (for just you) + taxes.
Looking at the 2 choices, which one seems MORE "stupid"? Of course, YOU get to have complete control over how YOU share the data. I guess if that is more important to you, it is an easy choice.