Also, have you been in a music video and done that? I'd like to know why.
It's well documented in many interviews that it all started with guitarist Pete Townsend of The Who, who accidentally broke the headstock off a fragile and expensive Rickenbacker electric guitar when he was performing with The Who in a hall with a very low ceiling over the stage. He lifted the guitar up over his head several times, and each time it banged headstock-first into the ceiling. Once the headstock broke off of this expensive guitar in mid-concert, he made a great show of smashing the rest of the guitar in front of the audience, out of frustration. The audience responded so enthusiastically that he decided to make this a regular part of The Who's stage show.
Soon, however, the drummer and the bass player in The Who decided to also smash their instruments together with Townsend at the conclusion of the show. Obviously this was interpreted as extravagant and decadent (as was the behavior of the members of The Who offstage and elsewhere in public as well) and delighted a certain segment of their fans.
I remember a few quotes that I have read in Pete Townsend interviews over the years. First, he has frequently expressed regret over smashing some rather expensive instruments. When asked about his attitude toward his instruments, he replied, "I don't have a love affair with the guitar. I play the *#$&^@& thing".
The other quote I remember was rather tongue-in-cheek, made in a radio interview with Terry Gross on her Fresh Air program. He said something like, "When I smash a guitar I want to make a certain statement."
Gross asked, "What statement is that?"
Townsend replied, "The concert is over."
Yes, there can be a meaning. As I recall from the documentary Amazing Journey, Pete Townshend of the Who says he came to see breaking his guitars as an act Auto-destructive art. He had attended lectures by Gustav Metzger while at art college. Also, if I recall correctly, he describes a lecture he attended where someone sawed a double bass in half.
In the case of Pete Townshend, the initial incident seems to have been an accident, but smashing his guitars became a kind of performance art, and part of the show.
Here is an interesting quote as to why Jimi Hendrix destroyed one of his guitars by setting it on fire. It may shed some light on why rockers destroy there instruments.
It is also interesting to note that one of these guitar set to fire actually survived. It is now owned by Dweezil Zappa. You can see something interesting here.