I think there's a big difference between 30-40 domains not being used for an honest reason, and 15,000 domains purchased for the specific purpose of reselling them at a higher price. And that's only 15,000 bought over a two-day period. How many does he own in total?

Given the numbers here, I'd say that any random parked domain you find is statistically far more likely to belong to a domain squatter than a legitimate "I have this crazy idea that I'm not sure if it'll take off" entrepreneur.