I can remember back when ezine publishers rarely asked this question.
Times certainly change.
Right now, it doesn't matter that you believe the subscribers of your widgeting newsletter are a sound target for a widget manufacturer. If you don't know your demographics, you are at a distinct disadvantage in regard to your competition in other media. The pool of online-only advertisers willing to do CPM deals has shrunk down to a puddle. The majority of legitimate offers coming through right now are from media houses which would love to use email newsletters as part of the mix, alongside TV, radio and print. It's time for us to deliver what advertisers have been asking for all along.