I knew a somewhat obese guy who sat on his guitar while he was very drunk. Now that is extreme... The guitar didnt survive...
I don't think it is reckless at all. I push as pull against the neck to get vibrato all time. It really does nothing to the neck. you have to realize that guitar necks have much more tension on them than you think and wood is quite flexible. By pulling a bit or pushing again the neck to change the pitch or get a vibrato sound doesn't add much tension at all to the neck. Also, if you have ever seen Jake E. Lee (Ozzy Osbourne, Badlands) his able to achieve vibrato very well with his guitar. He has been playing the same guitar since the late 70s at least.I just cringe when I see people using their guitar neck as a whammy bar by holding the body and bending the neck to get some whammy or vibrato effect.
Yes, I have tried that... when I was a teenager (a trillion years ago </hyperbole>).
But now when I see people doing that I get a somatic aversion that ties my stomach in knots. I guess I feel for the guitar and after performing my own set ups, truss rod adjustments, saddle piece intonation, string height, and all that myself for my instruments I just think that it is a reckless move. Sure some people smash their guitars on stage which is also a waste of sorts and by now totally cliche. Yes, I do still like seeing footage of the Who smashing up their gear and even more so like watching the footage of Hendrix burning his axe at Monterey Pop but those innovations of performance are not innovative anymore </tangent>
Does it bother you to see people using their neck as a whammy bar or for vibrato? Do you do it too?