Organic growth vs investment is an interesting question. To play devil's advocate a bit, think about their competition. What if a competitor with a slightly i

Organic growth vs investment is an interesting question. To play devil's advocate a bit, think about their competition. What if a competitor with a slightly inferior but "good enough" service invests a lot of money into sales, marketing and business development, then eats their market whole? What if a large real estate firm with deep pockets more or less copies the service? What if craigslist suddenly decides to redo their apartment listings? As an entrepreneur, you need to count on your competitors being absolutely ruthless. Having already taken Y Combinator money, they're now obligated to steward that investment. That implies a couple of things -- growing fast enough not to get outpaced, paying for some benefits for yourself (what happens to YC's investment if these guys get really sick?), and building some cash reserves to weather variations in the market. They're lucky to be faced with the dilemma to be sure. And for whatever combination of reasons they've decided to go for the investment. It's a pretty modest size, and they'll be able to retain control.