This oped in today's Washington Post, by Robert Samuelson, does a good job of explaining why some people are worried that President Bush's Social Security proposals might have adverse unintended consequences. Samuelson's article has a good title
Welfare vs. Wall Street The bottom line:
What looms is a massive expansion of government power over Wall Street. To be sure, it would occur gradually, over decades, and its outlines are murky. The irony is that it comes from "conservatives."