I don't know much about VC, but just in my "main street" experience people always get shaky before stroking a big check. When it comes time to sit down and send away a lot of money on a business, a piece of property, whatever, that is when the doubt begins to creep in.

It could be that they loved seomoz but weren't that excited about the industry. Or, like Rand mentioned, they were nervous about the market. The July numbers probably wasn't the reason they pulled out, but it probably was the excuse they used internally to rationalize the decision.