Jim Novo's a smart guy. For years now, Jim has been providing solid advice on the strategies and math needed to advertise profitably. His recent post on share vs. profitability is spot-on for direct markers.
We've written about J. Scott Armstrong's research before ("Business Is Not A Sporting Event", 12/13/06) Jim's post on Armstrong is worth reading (and not just because he backlinks to us). Check it out.