This is a question that I've been asked several times over the past few days, and I think the short and simple answer lies in the nature of your site. If you had something like payday.com then yes, it would be a very good proposition and make you a great deal of money. However, what about something like mynocreditcheckpaydayloans.com (thanks for letting me use you as an example guys)? Not so much. While a site like that could do a solid amount of business through PPC, organic search, or e-mail marketing, the chances of someone typing in that domain are minute. Therein lies the litmus test for redirecting any sort of domain to an affiliate program; if you think it will get a lot of type-in traffic, then redirect.
The most obvious caveat to this is that if you were to build up the authority of a site that didn't turn out to be (cough, cough) user-friendly, then redirecting to a payday loan affiliate program such as ours could work. We definitely have seen some success among a few affiliates that have gone that route, so it isn't to say that only type-in traffic quality domains make sense to redirect…it is just to say that they are the best candidates for such types of traffic transfer.
JoeSinkwitz