If you're going to limit the discussion to startups (I did not), then we need to have a different discussion. I imagine all Facebook employees with an employee number less than #1000 are quite happy with their options. As with all things investing related, risk is proportional to reward. So, those 70% that aren't paying off are offsetting the 30% that are paying off massively.
If you don't want to take this risk, choose a different industry. Traditional corporations issue options all the time that pay dividends that consistently net positive value. You may only get a few hundred/thousand per year, but you can depend (somewhat) on the income they generate.
Typically the case? I'll wager that greater than 70% of startup employee options never pay out.