How common are multiple point failures?

My friend just bought an airplane. He did the prepurchase inspection
himself. That's not as bad as it sounds - he is an A&P/IA and has
owned and restored many airplanes. The plane was an older model light
twin and he got a great deal on it.

On the flight home one of the nav's (the only one with GS), one of the
comm's, the DME, one of the EGT's, and the Mode C all failed. This
was after he completed the inspection and wrote the check. Everything
worked when he started the flight home.

When he bought his last light twin several years ago, he had a similar
streak of failures bringing the plane to his home base for an
inspection. However, that time the owner was with him, and they had
not yet negotiated a price. Once again, everything worked when they
started the trip.

A different friend of mine ferried a light complex single from Texas
to the East Coast. They started the trip with a full IFR panel (dual
nav-coms, DME, ADF, etc) and finished with a single radio and
transponder - everything else had failed enroute.

Do I simply know the wrong people, or have others had the same
experiences?

Michael