Nope, I haven't succeeded with Clickbank yet, but that is only because I have barely had the time to promote or choose an affiliate product. So I guess I am part of the 3/4 who fail, but seriously - you have to have drive or be very lucky in order to make cash
with clickbank. Just signing up isn't enough, you need visitors, a landing page, splash page and promote it endlessly to get sales. But in the end, you will reap the benefits for your hard work and probably make some $100 per day if your really driven. Laziness is not an option!