the junky old spare power supply that I got from a guy with a big box full of laptop power cords ($5 each yo!) fell apart recently.
first, I lent it to my sister, who has a macbook *pro* which requires a big meaty 65w brick to charge and run at the same time. so this little guy apparently takes a long time to charge her battery. anyways, long story short, it got kinked and is now held together with tape, that promptly melted. real ul-listed electrical tape, apparently
but the thing I really wanted to show was inside the magsafe connector itself. As if to say "oh god just let me die" today, when I pulled the cord out of my bag, the cover was missing. but it still works
there's a little id chip in there (mainly so your 15-pound macbook pro supercomputer with three graphics cards and an octocore processor doesn't fry a cigar lighter adapter) and also a serial number. This is why you can't just replace the cord north of the brick, but have to replace the whole power supply when they break down. Otherwise, you could get your id chips mixed up and overload a tiny power supply. I might do some more prying and pulling later on to get more of that flex pcb exposed
comparing the old magsafe to the new (well, newer, a 2010 model) that came with my net book. I like having a couple spares about but I only have two in 45 watt variety. the most popular are the 65w IME, but I like the tiny ones!