It seemed to me that the fundraising is mostly to make a bunch of noise. When your company is growing by leaps and bounds, and the only limiting factor is that you're cash-strapped, a round of this size makes sense - not with the numbers/usage Quora currently has. Most of the reasoning that Adam mentions seem rather frail. Doing a funding round just to post a better-than-you valuation isn't what they should be focused on at the moment.