All of the investors are invested in other Bitcoin-related ventures. OpenBazaar has the potential to get people to actually spend Bitcoins, which people don't r

All of the investors are invested in other Bitcoin-related ventures. OpenBazaar has the potential to get people to actually spend Bitcoins, which people don't really do now. That then has the potential to increase Bitcoin's value, which will help their other Bitcoin-related investments. For example, Andreessen Horowitz has invested quite a lot of money into Bitcoin mining operation, 21 Inc, who in turn have mined a lot of Bitcoin. If Bitcoin's price goes up, the value of 21 Inc's holdings go up.