While I think the concept of scalability in careers is very interesting, I'm not sure Taleb's "look at everything in the world in the context of my last book's title" framework provides the right perspective for the discussion. While the true home runs are indeed low probability events, risk/reward is quite asymmetrical in many scalable careers(i.e. there are no fat-tails to the downside). In the case of the author, the worst case is you spend a year writing a book, and receive zero revenue from the book. That is a pretty well defined worst-case, and is not particularly disastrous (assuming you can afford your expenses while writing).
Put differently, scalability does not imply high-risk. In the most literal sense though, non-scalability does imply limited potential reward.
I agree this is a good topic and it shouldnt just have to be centered around probability.
The scalability idea points to the fact that starting a company while your working for someone else is not a bad idea. If you can make 100K-200K doing a 9-5 job then you should keep it and keep trying to start businesses until you succeed.
Live cheaply and execute as many ideas as you can. Ie your job is your VC.
Now this is obviously not easy but if you can build the emotional and hard-working capacity for this I think its possible.
Put differently, scalability does not imply high-risk. In the most literal sense though, non-scalability does imply limited potential reward.