Plenty of people have written books that confirm/deny the efficacy of the Waterfall model. But in the meantime, there are far, far many more folks - by signifi

Plenty of people have written books that confirm/deny the efficacy of the Waterfall model. But in the meantime, there are far, far many more folks - by significant orders of magnitude - who have written software with the Waterfall model. Far, far more. The fact that it is still with us, and can still be used quite effectively sort of leads credence to the idea that those who can, do, while those who can't, teach (or write books about it).