This article seems to ignore the main argument I've heard: exit strategies are fewer in a recession. IPOs are out of the question and few companies are in an acquisition mood. So instead of growing fast and selling out before you hit your plateau, you have keep your traffic climbing until the market picks back up. That's really hard, esp. since founders have a tendency to get bored. I expect many will start something…
There is a hidden assumption in the above: it assumes that a startup's competitors are other startups, not established firms. Established firms have easier access to credit than startups. (They can fund new lines of business out of profits from existing lines of business, for example, which is a form of "access to credit" for the sake of this discussion, which is about starting new lines of business -- i.e., exploiting new markets.) This is a real disadvantage of startups relative to established firms, and the disadvantage gets bigger because of the economic downturn, but the disadvantage of being an employee of an established firm when lots of job hunters are in the market might get even bigger.
There are ways in which startups have been able to neutralize the funding advantage held by established firms. One big way is to be more agile. "Agility" means adopting new technologies and entering new market more quickly. Changes in technology and changes in markets and potential markets continue to occur during economic downturns.