I'm thinking of proposing a new rule banning the use of referral links of any kind, either for DH or other services (web hosting or otherwise).
I thinking banner referral links that are DreamHost-related is wise. If a customer has found the forum of their own accord (in otherwords, they have not followed a referral link) it seems unfair for DreamHost to pay for an unwarranted referral.
Third-party referral links seem okay to me, however, and here is a good example of why I think this: If a customer (or potential customer) asks for assistance in looking for a good book on web authoring, and I take the trouble to find a book and link to it in a reply, it seems reasonable that I should be able to add an affiliate ID to the URL. In this post, for example, I referred someone to some books that included my Amazon affiliate ID.