As I recall there have already been cases of cutting cables to move traffic to other cables which have better monitoring capability. But as for the lulz, I expect that even the most naive of folks who might do this understand that it would get them some serious prison time, and there would be a huge amount of effort put into catching them and making an example out of them. Not quite worth it I'd expect.

That said, we've had folks take sniper shots at power substations in California[1], which can cut power to big chunks of real estate.

[1] http://www.mercurynews.com/business/ci_26419083/pg-e-substat...