I'd feel better if the 300k/yr person paid 40% and the 30k/yr person paid 3%. Perhaps 2% is more fair. Contrary to Republican and some idiotic other's misunderstanding, Social Security is just fine, it needs no privatization in order to "save" it. It's OK until 2030 or thereabouts, just the way it is.
Mandatory 401k's aren't the greatest idea,
IMHO. Many people's 401k accounts have lost one half and more of their value because of the Stock Market's crash.