You actually do know who its going to, the mesage header has all of the recipeints in it... I find it more of an invasion of privacy to the receipents since the sender, if they pick a large number of people to send this message to, every iPhone or Blackberry user that supports group messaging will get this message INCLUDING the phone numbers of ALL the recipients on the header.
I feel that is the largest issue here. They are allowing someone to send out your information without your permission... They should set it up as a blind header or mask the other recipents actual number so others don't see it. And if they don't want to do that then simply INFORM YOUR USER BASE OF THE CHANGE TO THE TXTING ABILITY! I hate it when info is left out on what was changed in an update.
Also the simple fact that Apple impliments something that not all phones support so anyone who doesn't have an iPhone is more annoyed with it than those with the iPhone. As I noted on my HTC, I get a single message from the original sender and then I get random replies to that message from other people. I can figure out whats going on but some other users obviously get ****** when they find out some random person is replying to them and now has your number.
Jimmy, your suggestion is fine if your the sender... but I do not think it works if your the recipient of a group message. Simply said there needs to be two functions for this... Group messaging as it is now to make all of the teenie boppers happy so they can have an iPhone chat room, AND there needs to be a Mass message option that allows you to simply send the same message to a large group of people without it showing up with all of the other phone numbers attached. You shouldn't have to go dig for a group MMS setting and turn it off every time you want to do that, you should have that choice while composing the message.