Ear-candling has been demonstrated to be a complete and utter hoax, by CSICOP, the Committee for the Scientific Investigation of Claims of the Paranormal. The complete article was published in their magazine, "The Skeptical Inquirer." There are absolutely no scientific principles at work, the "vacuum hypothesis" is completely nonsensical when one looks at the physics of the process, which CSICOP demonstrated through a series of tests. The most damning test compared a burnt candle that wasn't even placed into an ear with one that was (guess what, no friggin' difference). The process is simple and useless -- a cone of beeswax is plugged into the ear, and the end is lit. Wax drips down from the wide end into the tapered end, which is similar in appearance but not identical to ear wax. This plug is removed and showed to the victim. They "ooh" and "ahh," foolishly unaware that they are looking at beeswax. Analyses proved that this wax came from the candle and not the ear, as it just doesn't even come close to the consistency of real earwax. This is yet another new-age pseudo-scientific hoax, and this is coming from a fan of Andrew Weil (I'm the fan, not the inventor of ear-candling). Stick with Q-tips and syringes.
If you want to see this for yourself, buy 5,000,000 ear candles, and amaze yourself with the 5,000 tons of "earwax" they produce. Those who insist that they did hear better (generally it's only for a couple hours) probably a)are excercising the power of suggestion on themselves, or b)their ears actually are a little bit "opened up" from having a fat cone shoved in them, and I bet everything seems a little louder after you've had a big candle jammed in your head for however long.
Ok, I'll even provide a c)...perhaps the heat indeed does loosen up the wax a bit, but there is no physical way for it to be drawn into the candle. So basically, the wax gets runny and goes deeper into the ear..perhaps.