Thanks for you questions, I think you raise important issues that need to be discussed more.
(1) Keep in mind that Social Security isn't just a retirement program, it's really a family protection program that includes disability coverage and survivor coverage. When evaluating privatization proposals, you should consider whether they provide a benefit should a breadwinner become incapacitated or die.
(2) Administrative costs for individual accounts are high because the account sizes are so small relative to the costs to manage them.
(3) Insurance programs need as large a pool as possible to minimize risk generally. Allowing the wealthiest or healthiest to abandon their commitment defeats the purpose of having a national protection program that binds generations. That generational tie is particularly important. Remember Social Security benefits your relatives who are in retirement now. If the young dropped out, it would be the old who would suffer.
