As someone who has worked with both types of programs, I am of the opinion that as soon as Social Security retirement becomes "means tested" we will be on our way, in an even bigger way than we can imagine, to serfdom and slavery and the peer/peasant society. It's the same reason I do NOT approve of members of congress not being paid salaries. It clearly sets up a situation of "I need it" or "I don't need it."
In the first place, enforcement and certification of people for Social Security benefits will become a complete nightmare. There will be thousands and thousands of critics lining up to say, "What? They're receiving Social Security? What business do they have with two cars? A new bedspread? Expensive medical procedures? " The classic example is those who wish we had "food stamp police" to stand in the groceries and forbid people who are receiving "our tax dollars" from buying junk food. Not realizing that to enforce such silliness would cost far more than the whole program in general.
Verification will give the government certifiers huge amounts of access to private accounts and information. We will have to set up punishments for those who falsify and try to cheat the system. There'll be a few of those.
There will be a large number of older people who will try to starve and get by, without accepting this "welfare." It will become a point of pride and people will be able to feel superior if they're too rich to have to get Social Security. It'll be another way to judge, belittle and feel superior for those who are born lucky.
Means testing for Social Security is pretty much another way we could jump in here and make our country totally crappy, another way to allow the haves to lord over the have nots economically, and make them feel virtuous about doing it. I think the whole concept of Social Security retirement for anyone who's paid into the system, regardless of means, is an excellent idea, and has gone a long way toward making the program the most popular in our government's history.
I believe that taking social security out of more and more of a person's earnings, not just the first so many thousand, might be a way to go. After all, we do have in this country a lot of people who are making out like crazy, and are raking in the money obscenely. I'd like to see us put more of that money into the general Social Security pot. But never do I want to see "needing it" as a criteria for Social Security retirement.