401ks are not Ponzi schemes because:
1. They are not deliberate frauds. Anybody who can read can figure out the fees and risks involved.
2. Buy in of new entrants is practically infinite, so the Ponzi dynamics do not really apply here.
And ultimately, folks have an option of putting their 401k in cash and choose not to participate in the markets.
It is true the most big companies have ended up with healthier balance sheets after doing away with the pension plans for new employees in 1990s. However, those new employees also benefited because they now have job and retirement portability instead of having to stay with a single employer for a dozen years or so.
