It is true that there are large stakeholders of XRP but this is not significantly different from Bitcoin. Furthermore, it's not in OpenCoin's best interest to cause the value of XRP to drop through a sell-off.
No small group of people have 99.9% of all bitcoins, and in fact only half of the bitcoin money supply has even been allocated. Even if the bitcoin creators mined up a significant portion of coins before other people got on board, that's still profoundly different to what's intended for XRP.