Haven't hit anything yet, most of the hoes I've run weren't able to. Most of the Cat hoes I ran had wedge lock couplers, so even though the coupler was there, the bucket was more or less in the same position relative to its pin as it would be without the coupler, never had a problem hitting a cab. I actually tried it out one day to make sure in my dad's 312, there was no way to hit it.
I ran a couple PC400's with Esco pin grabbers and 72" buckets. The buckets weren't terribly deep, but had a decent heel and were tipped with twin tigers. Came close with a fresh set of teeth, but I found out through observation in my off time that it I couldn't munch the cab.
I saw a Hitachi ZX450 once that had a nice cab guard on it and a PSM pin grabber. Took a look in the cab and there was a big sticker that said "Warning! Bucket will hit cab guard!" pasted on the cab glass right above the guage display unit. Didn't see any mangled steel on the cab guard, gotta assume the sticker did it's job. :drinkup