Have you ever soldered anything? Have you ever heard of micro soldering...or surface mounting? I'll keep this simple for you. It's uber light and small soldering, usually done by special soldering machines. Sometimes it's even more of high pressure stamp than an actual solder, but the outcome remains the same.
These micro solders create very small points - usually 2mm or less in size - and like anything that is put together, let alone mass produced, can and do break. Especially when they get hot then cold, hot then cold or if they are done poorly and take some abuse. Say the kind of abuse that can happen when they are subject to poor handling being shipped all over Gods green earth. If even one or two of these solder points breaks, it could be enough for the chip to vibrate all by itself. It can also be enough of a vibration to rub against something it should not, say a fan or a case.
But hey, you and the other trolls in here who are just so certain you/they know more than me or everybody else, go on believing that you are more than you really are. Now I should officially say, school has ended. Keep on casting!
*Edit* BTW I was not laughing at you, well at first anyway. I was laughing at the comments of macsaucer troll. But after you came out blazing like a troll as well, I am in fact now laughing at you both. Man up, eat your crow and move on. We all have to do it sometimes!