Dual agency is legal in New Jersey. In other states, even when dual agency is not permitted, a form of represetation that is some form of it, but called by another name, might be.
While I think that most Realtors will be upfront about all details and material facts about the property, I am still not a fan of dual agency. There are instances where it goes smoothly and works well for all parties. When there are no disagreements between buyer and seller, having one agent can actually make things siimpler and faster. There isn't another party to be contacted for mulitple discussions or appointment setting. My objection and concern with dual agency has to do with the fact that one person cannot serve two masters when the buyer and seller do not agree. What happens when buyer and seller look at the same factual info, but take differing positions? For which party does the agent negotiate?
While there might be a few bad apples out there, most Realtors willfully disclose all material facts about a property, and most make diligent efforts to encourage their sellers to provide full disclsoure.. A Realtor with an established relationship w/ their seller client will not disclose personal information about their seller that would be disadvantageous to the seller in negotiations. Nor should they.