I'm sure that many people faced this nasty thing: after you clone or reconfigure a Virtual Machine, OS reconfigures the interface because it has another MAC. I will not say that this is bad behavior, but what can you do, if you need to preserve the eth0 name and configuration?
In CentOS it's very simple - all you need is just to remove a string like "HWADDR=00:11:22:aa:bb:cc" in file /etc/sysconfig/network-scripts/ifcfg-eth0. That's it! Now even after you clone this machine or in any other way change the ethernet card - config will not be changed. Of course, in some cases there is a risk to face an IP conflict, but you're good admin, right :)?
Well, I don't use Ubuntu for server often, so I didn't look for a persistent solution. But what I do time to time, is just removing all strings from file /etc/udev/rules.d/70-persistent-net.rules right before cloning. It makes Ubuntu to forget, that some ethX name is already assigned for some MAC address.