Earlier quoted context omitted.
At the time this book was written, 37Signals couldn't keep a Rails stack running for more than a few hours yet, according to that old rant by Zed Shaw.
When Zed Shaw wrote that rant 37signals already had thousands of customers for its Rails apps (plural).
There's no reason to try to cover up the fragility of the early Rails web stack. That's in the past. It's much more stable today, with many more choices of software at all layers, than it was in 2006.