Update: It's up to Apple's discretion and I'm not sure if they are still doing it but, if you bring your frayed adapter into the store they may just give you a replacement. As long as it isn't to mangled and shows normal use.
Now I'm usually a big fan of Apple but some things they just don't get right. I got my MacBook Pro used, not a bad deal everything works great but noticed a bulge in the cable by the MagSafe connector. I thought nothing of it but I was still cautious, trying to not bend it wrong and eventually have it break. Well, over the course of a month the cable started to deteriorate. So much for being cautious. This last week it would only work if I held it just right. I had enough! I thought okay I’ll just get a new one. Sure, for $80 from Apple! What a waste of money when the only thing wrong was a bad spot in the cable. Okay so it’s a little more complex than that. The insulation was melting, the wires had poked through and started looking like steel wool. Not a good sign!