Helium hard drives
Hitachi (HGST) is going to create hard disks filled with helium. Theoretically, it improves a thermal conduction and also allows getting more platters into the same form-factor. Obviously, such disk will be more difficult to repair, at least because a distance between platters decreases. It is less obvious that a vent hole (aimed to equalize a pressure inside the typical disks filled with air when the temperature changes) must be closed.
Maybe incipient pressure changes will be compensated by the lesser viscosity of helium; however, it the more severe temperature limits might be introduced. Additionally, it is known that it is more difficult to hermetically seal a volume of helium rather than that of air, because helium better percolates through gaskets. Thus, we cannot conjecture about the lifetime of helium disks.