In the US you need to have an income of greater than $200k/year or assets not including your home of over $1 million in order to be an accredited investor. [1]
You don't have to be an accredited investor to invest in startups, but it does open up the company to additional annoying reporting requirements such that almost all advisors suggest staying away from such. From info on his own assets that he's posted in the past, it seems Dave's chosen to skirt said law himself, but it seems quite brash to (without disclaimer) push others to do the same.