Got me thinking about this one now. My immediate reaction was agreement to the statement about engines falling off if a big jet did spin, but then I thought about it some more. First, the rotation rates are probably going to be lower - big inertias to overcome with aerodynamic forces. Second, IAS will be low - the average airliner doesn't have fighter power to weight ratios and will almost invariably be at low speed at spin entry, either because the pilot stuffed up some low speed handling (e.g. Vmca) or generated more drag than thrust in the manoeuvre leading to the stall. The structural loads are dependant on dynamic pressure, i.e. square of IAS. The average airliner is designed to cope with, for example, an engine failure at max IAS that generates significant sideslip by the time the usual allowances for yawing moment due to asymmetric thrust, directional stability, and for the average pilot to react to same and apply corrective control have all been applied. The resulting structural forces would have to be pretty significant compared to those generated at the low speeds seen in a spin, even allowing for the higher sideslip angles, because they're proprotional to the square of the speed.
That said, the above relates best to airliners with jet engines: I reckon the gyroscopic effects on big propellors would be way more whacky, so I'd tend to agree with the earlier assertion about losing engines if you want to go spinning a C-130 or P-3.