I like the idea of the Paths series, though some of the points in this first article read like they could be written about most "emerging technologies". Anyway, I'm looking forward to the next one! The two questions about the PhD's do feel a little bit misplaced for a startup audience. Who here stops and thinks "Am I supposed to have a PhD to do that?", when setting out to start something new? ( )
I think a better question would be: How much math do I need to approach NLP in a way that enables me to be among the best? PhD is just an academic title and as such it is neither a necessary nor a sufficient prerequisite to approach NLP from a mathematical angle.
The best in what? If you mean pushing the boundaries of research, yes, then your path there will likely involve a PhD. If you mean building the best technology products, then being able to read, understand and implement the biggest recent advances is enough and usually requires far less mathematical knowledge.
(That was intentionally written generically since I think that it applies to more than just NLP)