Point of View Gone Haywire

It has been coming to my attention more and more lately that it is becoming acceptable in the literary world to completely ignore all the little rules that have been laid down in regards to POV. Why has this become a good thing to do? I don’t get it. One of the biggest rules of writing, well, perhaps not a rule but a big know-how, is not to switch tenses. Not only am I seeing this in young writers–which is probably rather common–but also in professional, published literature. A novel I recently reviewed went from first person past to first person present, and even dared to go from first person past to third person past in the middle of a chapter. What exactly is spawning this sudden change? It’s destroying literature I think. Has anyone else discovered this issue in any particular books they’ve seen?