The Society to Advance Media Professionalism states: “It is deemed unethical for media sellers to plan, negotiate, and place buys for their individual clients. This is considered a “conflict of interest.” Also, buyers will not plan, negotiate, or place buys for competing accounts. This, too, is considered a “conflict of interest.”
Clients, or advertisers as they are also called, are entitled to have their media strategies, rates, dates, and create held separately from their competitors. A media buying service or an advertising agency that handles two “like” and “competing” clients, is entitled to way too much information about both of the competing accounts. They will, very likely, make decisions based upon what one or the other of the competing accounts is doing.
It is unethical. Period. Enough said.