An individual can create multiple delegates and get stakeholders to approve them via deception. This gives the illusion that there are 101 unique delegates when in reality many delegates are in fact one individual. When you consider that multiple individuals could collude to create these faux delegates, it becomes obvious that gaining control over 51% of the delegates would not be that difficult.[/b]
Certainly more difficult than one individual or group running several pools and getting control over 51% hashrate. Imagine having around 10 delegates, imagine that the delegates have power proportional to the votes, imagine that 2-3 of the top voted delegates have control due to the proportionality factor - well, you get Bitcoin.
DPoS concedes that some degree of gravitating towards a few concentrated points is always going to happen, as was clear in the Ghash success, and later seen in NXT forging pools too. It attempts to regulate this behaviour by making it inbuilt in the protocol itself and trying to make sure that there is no more centralization than is necessary.