Quote from optioncoach:
The sillyness continues... You cannot even stop from contradicting yourself.
Naked puts are not safe, and it does not depend. Safe is reserved for treasuries and CDs, not naked options. Can you make money doing it? Sure any strategy can make money but there are no old-timers selling puts for a living, only those with stories about how they blew up after many years of making money.
At a minimum I would advocate put spreads over naked puts which shows a little more respect for the risk.
Naked puts are not an income strategy, but they're not the antichrist. They should be considered as a method of reducing cost-basis through assignment for the investor or as a spec on a reduction in rates/dividends for the trader. There are better volatility-trades.
Safety is subjective. There can be more risk in a short put than outright shares on vega, as in biotech, but they can be pretty innocuous when traded on large caps. Simply avoid selling stops on index.

