Public speaking and marketing himself have resulted in almost iconic status. He is still considered a guru but careful analysis of his work may uncover some flaws in the methodology. The Internet is like nothing else before it. Everyone that has attempted to bring 'old world' methodologies across to the Internet has failed or is in the process of failing. Advertising, Streaming entertainment, Radio stations even e-tailing.
Usability is no different.
With Nielsens strict Usability guidelines there was no room for 'whatif's' and 'maybe's'. That means we need to factor in a degree of irregularity. In a usability test this would be an incomplete task and fail miserably, but ask Amazon if it was a failure. If you couple this with varying business agendas it soon becomes clear that strict guidelines are not only prone to error but they may imbue a completely different message to your audience, one in direct contrast to your goals. For instance a hip radio station needs a site, but under strict usability guidelines the page should download relatively quickly meaning that graphics have to be kept to a minimum.