Most weekdays I take my wife to work at Starbucks and I'll sit in a quiet corner and get some blogging done or return some emails. I've become friendly with one of the other patrons because (of all things) the Mac. She comes in every day with her MacBook Pro, and I with my Air, and we'll sit in opposite corners and compute away.
About two weeks ago, she taps me on the shoulder to gain my attention away from my earbuds just long enough to ask if she could try the electrical outlet underneath my table. I asked if she was having power cable issues and she confirmed. She didn't have luck with the outlet just underneath her table (this particular Starbucks has quite an amp-le supply of outlets - see what I did there?) and wanted to test with the one I was using, since she knew it was working because I was connected.
I told her she wasn't disturbing me and that she could certainly try it out. It didn't work. She tried another one over by her table and no dice. I asked her if I could see the cable for a moment, since I've had a long history with damaged Apple power cables due to office chairs, my four cats, or just plain simple abuse. Sure enough, the power cable became separated out of the rubber ferrule of the power brick. It was just enough to cause the circuit to become broken and it was barely noticeable without a close inspection.
I've been victimized by this exact problem once before. It happens when the power cable is wrapped too tightly around the plastic prongs that are designed to store the cable during transport. The solution to avoiding damage to the cable, and in turn, your power adapter), is to pull some slack out on the cable before you wrap it. You don't need a whole lot - usually an inch will do. When you're cable is wrapped neatly around the plastic prongs, it will look something like this:
It will probably take you a bit to get into the habit of doing this, but I assure you, it will be well worth it. Just think of the $79 you won't have to spend (or because one of our cats has an affinity for charging cables, $79x5!) to replace a barely year-old adapter.
I bet you're thanking me already.