Obama was against this invasion of privacy under Bush. Now his administration is greatly expanding the program. However honestly its really nothing compared to the IRS scandal is a much greater threat to the average citizen.
I have never been happy with Verizon requiring the last 4 digits of my SS# to upgrade a phone. Now they want the last SIX! This is unacceptable in today's environment where identity theft continues to increase.
What is the problem? With identity theft rising, as you have pointed out, possibly Verizon wants to make sure someone is not making a purchase on your account fraudulently. Possibly someone could have gained access to the last 4 digits of your SS# as that has been the norm in the past. With the addition of 2 more digits, it is less likely someone would have access to that information. Regardless, since Verizon already has that information on file, they are simply matching it to what is in their records.
Of course, if you don't want to give this information, you can simply create a 4 digit "billing password" which is different than the last 4 digits of your SS# to make purchases. This can be done in your MyVerizon account.