While this is true in many cases, the angel investor of today has generally got priority on returns from any sale of a startup today. It's very different from the publicly traded dot com bust according to articles I've read on the subject. If "the bubble" pops this time, some investors will be hurt if they can't sell the startup. However, if the startup is sold for what was invested, the people left holding the bag will be the employees working for little more that stock options and a dream of a big exit. Those people will have worked months/years and will get no return. Their shares will be effectively worthless.
Join a startup when times are good expecting times to stay good seems like a good way to get burned. (buy high, sell low) Joining a startup accepting that there is inherent risk in what you are doing is, as always, a gamble. (penny stocks) Joining a mid to large size company with a legacy code base that has to be maintained by some old master in a particular language/framework/architecture seems the safest route to steady income, but you'll never become really wealthy. (Bonds) Catching the hype wave and riding it into newer, higher paid positions has great returns until your wave turns out to be a dud. (Stocks) In 2005 it was web apps, in 2010 it was mobile apps, in 2015 it looks like machine learning. If you bet on HTML5 apps in 2010*, you struggled. Many did.
*Flame away HTML5 people. HTML5 didn't make $40000 a day on flappy birds and iFarts. I know those are exceptions, but employers eat that stuff up. Salary studies that I saw reflected this.