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 their instruments.
Distinguishing yourself in the colorful musical climate of 1967 wasn’t easy. Merely being one of the most innovative and exciting musicians to ever play the guitar wasn’t enough. Jimi Hendrix had to literally destroy the instrument. According to manager (and former Animal) Chas Chandler, Hendrix’s guitar carnage began during a European tour in early ’67. The performer had accidentally cracked his axe when climbing back on stage and decided to pull a Pete Townshend and smash the thing. It would become a repeat stunt, depending on Jimi’s mood and the moment. In March, when the Jimi Hendrix Experience joined a crowded British tour — which included the Walker Brothers, Engelbert Humperdinck and Cat Stevens — Hendrix and Chandler cooked up an entirely new way to get attention from fans and the press. And it had to do with a new song the Experience were playing at their shows, “Fire.” Chas, Jimi and rock writer Keith Altham were hanging out before the tour’s first show on March 31 at London’s Finsbury Park Astoria, when the journalist suggested that it would be cool if the guitarist played “Fire,” then actually played with fire. A roadie was sent out to buy some lighter fluid and Chandler concocted the plan. After the Experience concluded their opening set with “Fire,” Hendrix put down his guitar by the amplifiers and sauntered back to the front of the stage as Mitch Mitchell and Noel Redding continued to jam. While Jimi was distracting the crowd, Chas doused the Stratocaster in the fuel. Hendrix grabbed the guitar, knelt beside it and, after a few burnt matches, set it alight. Due to the amount of fluid on the instrument, the flames soared to a height of four feet, burning Jimi’s hands in the process. The emcee, rushing to extinguish the fire, also suffered minor burns. Although Hendrix was able to perform the finale on another guitar, he was later treated for his injuries at the hospital.
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.