Seth Godin has a great insight as to why "people don't buy your offerings," check it out. Godin is spot on when he talks about how testimonials, proofs, and even case studies don't work. Buyers (and this time Godin focuses more on B2B) don't care about you're proof - they worry about your story (does it resonate), they worry about what their boss thinks, they worry about; well they worry about whatever it is they worry about. They are (just like you) irrational creature - embrace the irrationality and make more sales.