If PG says "you should start a startup in a bad economy" it's simply a clever sales pitch, a spin on the current circumstances. Back in 2008 when this was posted it was presumably in response to the Global Financial Crisis (or "Credit Crunch" in the UK), I'm guessing it's being posted again due to the recent layoffs.
It may be the right time for you to take the plunge, but you should be reading this article with a clear head and remember that this is not an old friend giving you some sage advice, but someone who is incentivised to get you to take risks on their behalf.