I don't buy the valve spring issue either. I've fired motors with lots of valve spring pressure and flat tappet cams, never had a problem. I've also had motors not start or shut off early because of fuel problems, timing problems, trans lines leaking, over heating etc. but never wiped out a cam because of an incorrect break in procedure.
Sounds like a fly by night shop. What did they set the lash at? How much guide/retainer clearance? Coil bind clearance?
Tempest455
http://www.wauknet.com/douthitt/