I've OCed GPUs and CPUs, RAM and Mobo Buses. Never failed under OC, though i've seen a few die under normal conditions. I HAVE seen parts become less stable over time though! I've seen CPUs refuse to OC anymore (at least on the same Mobo). I've seen RAM just stop working (doubtful it was OCing more heat related) But fizz crackle pop? Thankfully none to date.
My best OC was my 720BE from 3.2 to 3.7 the AM2+ mobo I believe is definitely the reason I didn't get higher. Waiting on bulldozer to see it 990FX is in my future, then my 1090T should see the magical 4GHz barrier fall