Like I said I've never heard "flapping" on my Martin Logans, was told by a friend that he tought they could be pushed to flap.
I looked up the topic on the Tube Aslyum, looks like the wire on Maggies can come off the mylar and or there might be an alignment problem which can cause flapping.
http://db.audioasylum.com/cgi/search.mpl
The sound compression and beaming that M/L's might experience at high sound pressure levels is a warning to back off or pay the price.
When an amp clips it causes distortion, this distortion can and may cause speaker damage. I don't know if one can also damage the M/L crossover or step-down transformer, but the cone woofer sure can blow (see classified current listing).
Other brands of stats have been reported to "spark" or "arc" when driven too far and might even catch fire. Although these things seemed to of happened only in the late 1970's or early 1980's and not with current technology/brands.