What's that burning smell? Oh, my Mag"safe".
@Phil Gomme: "What on earth are these people doing to induce "dangerously frays, sparks, and prematurely fails to work." failures?"
In my case, just using it normally - and rarely away from a desk. You can see the results at http://www.flickr.com/photos/ian-betteridge/435275376/
Basically, the first generation of MBPs and adaptors suffered from three connected problems, all of which contributed to the power cable close to the connector melting:
1. The cable was thin, and easily bent, which places stress on the internal wiring.
2. The sheath over the cable leading up to the connector was too short, which meant that the most-often bent part of it was very close to it.
3. The area where the connector plugs into was the hottest part of the laptop - and in the case of the first generation of MBP, that meant very hot indeed (it was far too hot to actually sit on a lap in use). The heat was inevitably conducted along the connector to the cable, which further softened the sheath, allowing it to bend more easily and making internal shorting more likely.
It's worth noting that Apple has actually addressed some of these issues. Newer Magsafe's have much longer additional sheathing, which means the most likely "bend point" is further away from the connector and thus much, much cooler. Newer MBP's also run cooler, which again contributes to a safer cable. It's still not a good design, but at least now it's less likely to burn a hole in your carpet.
@Richard Cartledge: So am I "blaming someone else" too? This design was poor - that's all there is to it.