The market takes that into account. It's still a free market in the bigger picture. Opencoin can not control whether or not people purchase XRP. As of now the free market has assigned a value of around 50 XRP per usd.

Opencoin is a service provider. And ripple is the service. XRPs are a part of that service and people deem that they currently have value. That value is partly based upon the market deeming that Opencoin is both trustworthy and capable. Whether that is actually true or not remains to be seen.