Overclocking for me is and has always been to get into the subject, read and understand what it is all about. If someone does that and then tries very little can go wrong.
Whenever I order a CPU from the net I tell what series of CPU I want and the exact production number. Its a little special store here in sweden...
Most modern hardware will not fail due to overclocking. Settings a high voltage will give a high temp and thus autoshutdown the system. And anyone with heavy cooling that will manage to cool that already knows what it is all about.
I started with overclocking long before there were 100.000 guides on the net. Self-trained and has still never broken anything.
Lets say you buy a brand new A64 3500+, if it does not overclock well thats about it. It won't break, it won't die. Not now and not later. The only thing that has happened is that you know it can't manage higher speeds.
Still any overclocking is simple to do but you are taking the chances from it. But I still think that in todays modern world of PC's it is something very low-risk. Almost any P4 Northwood core will manage a 600Mhz overclock with standard cooling, very little voltage raising and almost no difference in temp.