With electric guitars, it's a common technique to bend the neck of the guitar with your hands to produce a subtle pitch change. It is often used with guitars without a whammy bar. Are there any noticeable side effects that come with doing this too much over time? Would this technique weaken the neck and cause it to snap eventually?
I have seen a nylon strung acoustic guitar neck snap doing this but an steel strung guitar has a truss rod strengthening the neck. However you may damage the neck anyway, or break the fixing to the body.
I do it on my warlock, occasionally but I keep it very minor. I would suggest not bending too far.
Actually, in that video it was the body that broke, not the neck. Also, this guitar didn't seem to be really great quality. I remember Tommy Emmanuel commenting on his neck-bending in a piece (on a Martin western guitar): "don't try that on a chinese instrument!".
You certainly won't be able to break the body of an electric guitar, but the neck or headstock... it's certainly possible.
Years ago I was friends with Adrian Belew, and I remember hearing him say that he once ruined the neck on a Stratocaster after repeated bending. But he kept on using this technique on other Strats.