Most went way beyond that, topped by Jeff Wolfe's 29 and Alma Litten's 22.  Some surnames had multiple entries (Aldous and Thomas Huxley) and I accepted two names that started with Z but had another Z and a Y in the name (Zyuzin and Zelazny). 

Some interesting results:  The total number of different surnames submitted was 70!  Of these only 9 were submitted by more than one person.  Saint-Exupery, Oxley, and Huxley were the only ones with three submissions.  The long and short of it was Jazy and Rozhdestvensky.  Some other familiar names were Bill Bixby, Ted Kaczynski, Serge Koussevitsky, John Cameron Swayze, and Wayne Gretzky.  Also of interest was the name Mark Loizeaux, the only name not containing a y.  Loizeaux is President of Controlled Demolition, Inc., which is know for such demolitions as the Omni Arena in Atlanta, the Dunes Hotel in Las Vegas, and the remains of the Alfred P. Murrah building in Oklahoma City.  There were no names with all three letters — x, y, and z — in them. 

I'll e-mail the list of 70 names to those interested.