This advice is right on the money. I've spent decades developing at a number of startups (including playing the founder at some), but I have preferred to keep a low profile. As a result I believe it has limited my opportunities.
That changed for me six months ago. I started a blog and have been speaking at conferences. All of the sudden I'm a hot commodity. Its a tough time to be introverted with your career.
There's a period of time which is beneficial. It's not about being secretive, it's about putting your head down and getting things done without interruption.
Five years is (in virtually any case) way longer than that should be. But three months? Great! Even a year, if you're really on to something. But after that you need viable interaction with your customers/users/prospects
I agree with both of you; it feels fundamentally egocentric to broadcast one's thoughts on the web. But it's been an interesting exercise for me on many levels.
The feedback you get from friends and strangers can be valuable - like this discussion. And clear writing == clear thinking. I find that in the process of writing I edit and re-edit my thoughts and sometimes change my mind. That's helpful in and of itself.
As for public-ness making it difficult to quit -- many people (PG included) have written about this . My goal in making my work public is not to benefit from this social pressure, though that would be a nice side-effect.
I want to document my hard work, and ensure that the good parts of what I work on don't die.