Fabian,
This is great information to share. One thing I've found
increases response is to make an offer of support to
the person I'm approaching.

Big list owners get approached every day
by people saying "promote my stuff"
and very few of them actually say something
like, "Please let me know if there is anything
I can do for you."

Too many people seem to forget it's a
reciprocal relationship.

To your success!
~Paul