Interesting study produced by Merkle on the behaviors and opinions of consumers on permission based email.  While I love these types of studies, I caution this as a market view of behaviors with such a small sample size (2,000), so take it with a grain of salt.

You can view a copy by following the link:

http://www.merkleinc.com/user-assets/Documents/WhitePapers/ViewFromThe%20Inbox2008.pdf