I find that groupon using most of its funding from last round to payout people questionable. I can understand founders wanting to cash out a portion of their e

I find that groupon using most of its funding from last round to payout people questionable. I can understand founders wanting to cash out a portion of their equity before going public. However, when you are raising money say 10 million to fund growth etc, what % is considered reasonable to pay founders before it raises red flags to investors?