I have a friend who lost a tower in a hurricane (Bob in 1990 or so).
He used those guy wire clamps, just like the telephone/utility companies
in the area. In the hurricane, one of them let go. I wondered how it came
apart, but Gary's explanation makes sense. In the 90 or 100 mph winds,
perhaps the tower stretched the guy wires on the other side enough to cause
the guy on the failed clamp to have a little slack. I don't know for sure
if that explains it, but like Gary said - "preforms stay attached even if
they go slack".
Incidently, I have used both cable clamps and preforms. When I was
in my early 30's, I didn't have an awful lot of trouble bending the 1/4 inch
EHS. When I put up my most recent towers (in my 40's), I decided that I'd
spend the extra for the preforms because a lot of things that gave me no
trouble back then are problematic now.
73, Dave Clemons K1VUT