The Keene Defense to the King's Gambit

The Keene Defense (1.e4 e5 2.f4 Qh4+) involves two early moves by her majesty, since after 3.g3 the queen must retreat. What is the point of this maneuver? The basic idea is to set up tension on the e-file while the pawn at g3 just gets in the way. The opening has been considered rather unclear for a long time, and the latest judgement, by Gallagher (presumably) in NCO is really open to debate, as we shall see. In my opinion, it is a thoroughly respectable defense to the King's Gambit which requires knowledge of only a few lines. While there are many good alternatives, there is nothing wrong with the Keene Defense as a practical solution to the problems posed by the King's Gambit.