The article the economic impact of the internet quote came from wasn't a scholarly article or his normal column, it was a fun, let's make some provocative predictions type article.
A "a fun, let's make some provocative predictions type article" sounds like something very unprofessional to me. Also there seems to be a suspicious pattern of claiming exactly that after such an embarrassing prediction is made. I doubt the same would be claimed if he had happened to be right about the internet and the information economy.