Yes I do shop at Sam's, and yes I find the process a bit "insinuating". Trying to shop at an Armed Forces Exchange or Commissary is the same way.
However - you still did not answer the question - What would you do to prevent account stacking ?
If criminals can be monitored with ankle bracelets I'm sure there is other technology for the providers to use. Part of our monthly fees are used for research and developement. The answer lies there.