Does Greg Mankiw Charge for Book Endorsements?

I just checked out Mankiw's latest post -- he still has nothing about current Monetary policy. What he did have, though, was what looks like a paid advertisement for Steven Landsburg's latest book, the same Steven Landsburg with whom this blog has crossed swords with in the past. What makes me suspect is that Greg Mankiw is a businessman first and academic second. Of course, we'll never know if Mankiw pimps his blog, but from Greg's description of Landsburg's book -- "it is much fun. Reading it is like having dinner and sharing a bottle of claret with a smart, creative, iconoclastic friend." it sure sounds like a bottle of claret wasn't all that Gregory and Steven shared...