Stock Valuation

Consider the opinion:  "Stocks sometime produce stellar returns for a period of time, but then they fall in value so dramatically at times that it makes me want to just avoid them altogether."  What do you think?

Would a stock that pays no dividends have any value?  What about a stock with negative earnings (a negative P/E ratio)?  What about a company with negative free cash flow?  What do you think?

These are two separate questions. 200 words maximum.