I know you generally can't link directly to a merchant's site when advertising on serps. But what about the content network?
you can link directly to the merchant as long as it is ok in their terms and conditions. i mainly do ppc and link directly to cj merchants and of course all clickbank you can link directly. content or search though is the same for the merchant ie if they don't allow search direct linking they will not allow content direct linking.
I thought the difference would be that Google only permits one ad for each top-level domain per serp--is there a similar rule for content network ads?
i did'nt think that was your originall question!! yes, I could be wrong but I am pretty sure content is the same as far as one ad per domaign rule goes. sounds like google!