Just my opinion, but I think the problem is with asking for referals.
I firmly believe that most of the techniques of modern (especially "internet" and most direct) marketing preclude the possibility of getting referals. Think about it: direct marketing is sent to people's homes. It is private and is written to take advantage of the seeming privacy of the commuication (why does all direct mail look like a letter? even on the internet???). In private, many marketers will promise benefits or make offers that would sound bizarre to anyone outside their target market. Most people wouldn't want to admit to their friends that they purchased a product called, for example,
Gimme My Money Now -- after all, what would their friends think of them? (that they're greedy or desperate or both.)
I'm not saying that
you are marketing this way, but it's the standard that you are likely being compared against, especially if you are offering a free report on the internet.
If you want to grow by referals, you may want to look into marketing theory that is designed to enhance word-of-mouth. You'll find some similarities with direct marketing, but also many key differences.
Best,
Phil
The Secrets of Word-of-Mouth Marketing by George Silverman