I think I could make a pretty good argument that delegates' "real world" identities being known by the community doesn't really matter or prevent a "Sybil attack". Imo, what would constitute a "Sybil attack" is the collusion of delegates' motives. I'm also pretty positive that the colluding delegates wouldn't "harm" the Bitshares' ecosystem, but instead use their power to manipulate delegate elections to capitalize on the delegate positions. Everybody can know everyones' name, but it's impossible to know their true intentions.
Any block chain has the problem that a few big players can collude, whether they are large stakeholders or large hashpoolers. We dilute that down to under one percent influence per delegate, max.
Then there's the question of what they can collude about. We can all observe whether they are performing their very limited block signing job to spec or not. We can look at their published price feeds. They have no other power.
That's true that in all blockchains stakeholders/hashpower can collude, but they can only collude in a one-to-one proportion to their stake/hash. Since approval voting is used in delegate elections, I maintain that large stakeholders can effectively collude to a multiple proportion of their stake. Whereby, for example, 20% of colluding stake can disproportionately influence the elections of more than 20% of the delegates. This leads to a coalition of a few wealthy stakeholders being able to determine the outcomes of the mass majority of the delegate elections. This is especially true considering that voter turnout of smaller stakeholders will be lower than the voter turnout of larger stakeholders. As I said previously, it would be the intention of the colluding wealthy stakeholders to not harm Bitshares, but to elect delegates from which they would derive monetary gain in excess to their proportion of stake in the system at the expense of all other stakeholders.