For people trying to draw false equivalencies between buying Apple stock, buying lottery tickets, etc I think it's useful to look at the difference in circumstances and how _close_ Garry was to joining.
If you compare this to Apple stock it would be like if you had the cash in your bank account and your stock broker called you up and said "You should buy 1000 shares of Apple stock. In fact, I'll just give you 1000 shares of Apple stock, there's no risk to you". And you said no.
Or if someone said "I'll give you this lottery ticket, do you want it?" And you said no.
Now obviously, not many people find themselves in such a situation. But if you're a developer this situation isn't _that_ uncommon. i.e. you have a friend from school, or a someone you used to work with that is starting something new and asks you to join. This percentage goes up the "better" school you go to and the companies you join. i.e. I'm sure a large percentage of MIT/Stanford CompSci grads and early Goog/FB engineers know someone within 1 to 2 degrees of separation that have started fairly large companies.
Probably the most sure way to wealth (50M+) in modern times right now is to go to a good CompSci school, join a larger hot startup 200-500 people, spend a few years solving hard problems, getting a good salary and building a strong network. Then when one of your network starts a company joining that company as employee For 1-5M the surest way is to join a 1000+ employee tech company as an engineer.