>It's like signing a contract where someone else has the ability to change the fine print after I've signed it.

I don't disagree with your points about government access to this cloud information ... but this point would carry a lot more weight if these services didn't routinely get away with unilaterally changing their privacy terms.

I also really doubt people have well-formed beliefs about exactly which privacy rights they are giving up for these services, and government agents would probably be in a lot more trouble if they misled you about which rights you were waiving.