It's just anecdotal evidence, but I talked to a CEO that had just closed a deal with his A round from Kliner Perkins in August or September 2008. When it came time to fund the deal, the partners at the VC firm made the capital call and the LPs couldn't fund. So Kliner Perkins called the CEO and told them they had to cancel the deal.
The CEO had to make big cuts, couldn't pay rent on the building, etc. He eventually sold the company, but I wonder if it or others would have been IPOing around 2014-2015 if they had gotten the funding they needed.