I generally agree with you that investors and founders mitigate their risk through diversity and networking. However, I wouldn't single out employees as "the only one who really loses when a startup fails." Like you said, choosing a Google-like startup is tough, and most founders believe theirs will be incredibly successful when they hire early employees. But I can think of at least one example where the employee of a failed startup will have benefited greatly, possibly more than the investor and founders.

Imagine an employee who chose the startup because she passionately shared its vision, and the position available was exactly what she wanted to be doing. She worked out a budget so that her family would be fine with the lower salary. She gets to do what she enjoys in a fast-paced environment learning many new skills alongside others who share her vision. If that startup fails, she's out of a job, and the equity she earned is worthless. If she was paid enough to stay within her desired lifestyle range without taking on debt, and she enjoyed working at the startup much more than she would have enjoyed being a cog in the BigCorp machine working on projects she felt indifferent about, then I believe her risk as a startup employee was relatively low.

Opinions will obviously vary depending on how important compensation (after a certain threshold) and prestige are versus working on what you want.