Many good points in here...
The thought/rule to plan on only 2 of 3 possible income streams during retirement is huge. I'm one of the lucky few working a job that has a defined benefit plan, plus I'll have my 401k/IRA accounts, and what is left of SS. I'm hoping to get a 4th income stream squared away as a fall-back plan. I hope/wish to retire as early as possible because my job is higher stress but it has great pay and remarkable health benefits (that I can elect to continue into retirement, I just have to pick up the full premium). I'm still early in my career but as of now I may be forced to continue the rat-race just to ensure the continuance of the health benefits. My wife's job offers no realistic retirement. There's a deferred compensation plan but so far, over 10 years into her career, and she's built up enough balance that she will see about $50/mo benefit. I anticipate she will bring in $500/mo at best.
One wise thing point out in the thread earlier was to watch the tax-deferred vs tax-paid retirements (Traditional vs Roth). You will likely be in a lower tax bracket during retirement so for many cases it will be beneficial to have tax-deferred (traditional) 401k/IRA balances to draw from, but at the same time, the versatility of some Roth will also be good. There are no RMDs for Roth so if you find you don't need the income and/or you need to keep your income levels lower you can stop withdrawing from the Roth. Or, if you want to maximize withdrawals while minimizing taxes you can draw on your tax-deferred accounts right up until you would push into a higher tax bracket then take the rest as tax-paid (Roth).
Last point I would like to make. Don't completely rule out SS. SS is still very alive and well, and while the boomers will definitely draw it down, it's doubtful it will completely go away, the benefits will just steadily be reduced over time to keep it solvent. IIRC, the mass publicizied insolvency of SS isn't because it's out of money, or because the government stole from it, it's simply because the payouts have begun exceeding the payments in. That means from here on out the balance in the pot will be dropping from it's peak, it isn't going negative. That being said, I want to point you to the first part of this response. Only count on 2 of 3 income streams. I have a pension, 401k, and SS. If SS isn't paying out much I still have the other 2.
And oh yeah, the government won't nationalize 401Ks. Won't happen. The would much rather nationalize your bank account because there is realistic value in that. Your 401K owns a piece of paper that entitles you to the earnings a company or a debt. It does no good for the government to nationalize it; they wouldn't be able to sell the holdings and make money from them because the act of nationalizing them would immediately cause the real value of those holdings to plummet.