All sorts of things will void the warranty on your Apple products. With their Mac computers especially you need to be careful along with accidents like spillages of dropping the things, you'll not be entitled to a shiny new Macbook if you upgrade the ram or tinker with the insides in any other unauthorised way. One of the more surprising ways you can void the warranty, however, is by smoking near them. Yep, if you light up within the vicinity of your Macbook it will void the warranty, which is surely the bane of many highly-strung freelance journalists across the globe. The reason for that is Apple employees are advised not to work on such computers, because of the potential dangers of second hand smoke. The notoriously health-conscious Steve Jobs explained nicotine is on OSHA's list of hazardous substances and Apple would not require an employee to repair anything deemed hazardous to their health.
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/