Safe to lay tower on side?

Would there be any long term problems by laying a tower computer on its side (like a traditional "desktop" orientation).  In my case, it is an Inspriron 660s. When stood up as designed (tower) on its rubber feet,  the left side has no vents.  I'd like to lay it on that side.  It would also the only usable nonn-tower way to accommodate the optical drive tray.  The right side (facing it as a tower) has a large vent for the CPU, and would then be up.  Since the bezel is flared out, I would need rubber feet to stick on the left side, so the computer would lay flat, and keep the bezel from bearing weight, or scratching the surface its laid on laid.

Are there reasons I shouldn't do this?  Thanks in advance.

Here are good views of the various faces of the chassis.  http://www.walmart.com/ip/Dell-Inspiron-660s-i660s-2308BK-Desktop-PC-with-Intel-Pentium-G630-Processor-4GB-Memory-500GB-Hard-Drive-and-Windows-7-Home-Premium-Monitor-Not-Inc/21009310