An alternative datapoint - I have a charger that's not yet frayed, but it is starting to get intermittent - sometimes I need to wriggle the wires where they go into the mag safe connector.

That's the original charger for my 2006 black MacBook. It was in daily use by me for work until I got my mid 2010 MacBook Pro, and was then used as a "home machine" by someone else up until early this year.

The charger from the 2010 Macbook Pro is still working fine (but I'll point out I left that charger at work almost all the time, and "borrowed" the 2006 one when I needed to top up at home).

I suspect a difference is that I never "wrap the cable round the hooks", I just loop the cable up loosely and drop it all in my bag. I do the same with my iPod/iPhone cabes, and I've only ever had one of those fray (and I suspect that was one that got borrowed a lot). I wonder if this is a "you're holding it wrong" design oversight, where they've had lots of people using and testing them, but all in very similar ways which are not the only way they're used outside Apple?

Yep, I think this is it. I also have 5 years old MBP with the original charger, and it's still fine. I'm not a very careful person, and in general never wrap cables in loops, just cram them in the bag. Sometimes my cables get impressively tangled, but I think I'm still actually saving time by skipping the meticulous wrapping every time I take off (at least twice per day).

So maybe if you stop taking "good care" of your charger, and stop wrapping it in a tight loop, it will actually last longer.

That said, a lot of people seem think you're supposed to wrap the cables. After all, the MBP charger has built-in hooks for exactly that purpose. The charger is badly designed if wrapping the cable around the provided hooks causes it fray very quickly.

If they did usability testing, then the first thing they probably did was train the sample users. It's possible that fixed the test so that they never see the use case we're describing.

Probably not even "fixed the test", it might be something as innocuous as "Steve always walked around with the cables just looped up, not wrapped around the hooks", so that's what everybody else in the "sample users" group did too.

I'm on the third charger for my 2011 Macbook Pro. One of the broken ones has a slightly frayed cord which I repaired with tape, and I don't think it's the wire that broke it (though I admit I can't be sure). The other one has a completely undamaged wire, and yet also stopped working.

I really think it's the internals that are too fragile.