Most of the top tier domain name brokers are buttoned up and trustworthy. I would say this is the case for the vast majority of the best brokers. Tessa Holcomb from Igloo.com operates one of the top brokerages and she made a good point on Twitter yesterday:
Great Advice! When using a domain broker, they should be performing your due diligence for you but don’t assume they…https://t.co/hUnGSjpQ4e
— Tessa Holcomb (@tessa321) January 3, 2017
When buying a domain name via broker, the buyer still needs to perform the critical due diligence that is required of any domain purchase. Most domain brokers know their clients, but some likely don’t check the complete provenance of a domain name. Many brokers do proper due diligence before representing a domain name, but sometimes their good clients may have inadvertently acquired a domain name that isn’t “clean.” It is possible that a domain name is not rightfully owned by the seller, and the broker may not even realize it.
On most transactions, the contract (if one is even used) is between the buyer and the seller. This may mean that the broker has no legal obligation to the buyer should there be an issue. Of course there could and likely would be reputational damage to a broker who has brokered a stolen domain name, but it might not mean much to a buyer if the domain name is taken back or if there are any legal troubles in the future.
There are many trustworthy and exceptional domain brokers in the domain business, but it is always important for the buyer to perform due diligence rather than assuming the broker did it.