I have marketed products outside of the IM niche for a while now and I'm just now planning to launch an IM product. I refuse to show income proof... if I loose a few sales because of it, no big deal.
I prefer to focus on the quality of my copy instead.
Anyhow, my question still stands...
Why does income proof matter so much to you?
This is not a general question. I want to know your own personally specific answers.