And it would be true, but that is the flaw of bitcoin. People see it as being valuable as only compared to "real" currency. However its strength will save it and that is that it is p2p and works best p2p.
No worry about the market being cornered in an obvious way like the Hunt brothers tried to corner silver years ago. Bitcoin has value because it is scarce and it is easy to exchange and private. A cornering of bitcoins would keep them rare but would take away the other value of ease of exchange so blatent hording would increase scarcity but drive down the price because bitcoins are useless unless they are used as currency, unlike gold and silver which would still have value even if they were never used for money or for investments. Any hording would have to be done in secret or blamed on things like technical problems, server upgrades or "hacks".
Lucky for people who trade, mtgox is not associated with a tight cabal of French / Anglo friends based in Japan who were in on bitcoin from the beginning. Oh, wait....