But it's not about getting "utterly screwed". It's about making a rational decision that some things in life are worth more than financial reward.
Working at a startup has a multitude of non-financial benefits. You'll work with the latest new technologies. You'll play a key role in a small team. You'll be forced to learn all kinds of new skills. You'll meet lots of people. You'll acquire a sense of ownership and confidence that you may never feel when working in a large corp.
If you've got a family to raise and you're worried about your retirement savings, by all means, follow the math and don't expose yourself to the near-certain financial ruin of a startup.
But if you're young, adventurous, or simply value interesting work over a high salary, it can be a lot of fun to get utterly screwed with your measly 2%. I enjoyed my last shot.