Bitshares has already had a Sybil attack occur earlier this year when it was uncovered that an individual named "sfinder" actually controlled the
TOP 5 DELEGATES!The truth of this matter is, that as everyone knows who was around in 2013, Bitshares was originally going to be PoW. The Bitshares' devs only decided to switch to PoS after they saw the success of NXT. In a flawed attempt to look original, they added "delegates" to PoS which effectively destroyed it by adding centralization and opening it up to the aforementioned Sybil attacks.
Sfinder was found and voted out successfully.
It is almost impossible for full pay delegates to be the same person. Unless they are superhuman and able to complete multiple jobs at the same time. You can view the work delegates are doing. They have to be transparent and productive or they are voted out. It's simply not possible to all be the same person because 1 person cannot do 101 jobs. And there are huge incentives to not do this.
Delegates are one of the great features of BitShares. It's creating a thriving community and a whole new type of decentralised organisation. Not to mention the unique identity verifying features being developed. DPOS is an amazing, fascinating and powerful invention which is going to re-structure society itself. Constructive criticism is always welcomed, but please keep it real.