Assuming 3% returns above inflation, that's $120k a year...and at a tax rate of only 15%, since it would essentially be all dividends and capital gains. Since most people have already paid off their houses in retirement, where would it all be going?
In my opinion, if you're going to have a fully paid-off house and don't live in a high COL area, $1M is still sufficient for a "middle class" retirement if you can live frugally.
It doesn't work quite that way.
Lets say you have $1M of net worth. And lets say you have a typical house at $205,000 (Nov 2014 median price of sold homes). So, your retirement account balance is then at $795,000. 3% of $795,000 is $23,850 a year. And like Engineer said, this is at your full tax rate since most people have their retirement balances tied up in pre-tax accounts.
While it is doable, $23,850 pre-income tax just doesn't go very far. You'll have to pay a few thousand a year in real-estate taxes alone since in this scenario you own a house. So lets say after income tax and property tax you are at $20,000 a year. The cheapest Medicare plan is about $1260 a year and prices just go up from there. Typical heath care costs (deductibles, etc.) are about another $3500 in retirement. So you are left with ~$15,280 a year to live on ($1,270 a month).
Sure that is possible, but $1,270 a month is not that much. And that is assuming a pretty generous 3% return over inflation. Many people start getting conservative in retirement investments and probably return closer to 1% to 2% over inflation. Or if the stock market takes a dive, even for a bit, you'll average far less than 3% that can be safely withdrawn. Social security, if you qualify, is your saving grace in this case.
A $2M nest egg goes far, far further than just $1M. And if you are talking an early retirement, $4M is a pretty comfortable amount. $1M is doable, but really is a terrible risk in case something goes wrong.