The real security concern with VMs is duplication
... if you clone a bunch of VMs but they start with the same entropy pool, then generate an SSL cert after clone, the other SSL certs will be easily predicted.
Yeah, I encountered that the other day. Built a VM, took a snapshot, did some stuff, reverted, did the same stuff. I was testing a procedure doc I was writing. Part of the procedure was creating an SSL cert, and I got an identical one on both attempts. That seems a little fishy to me; I would expect the certs to be (by the standards of cryptography) very similar, not identical. With that said, I didn't actually generate the cert myself, I ran a script (which I didn't write) to do it. The script might be using the same random seed or something. Or it could be a characteristic of moznss.
Feeling good about your EC2 instances, eh?
No shit. It might be worthwhile to use your desktop or some other hardware you control to seed your VM's PRNG with higher-quality entropy. That way, you should at least be able to avoid collisions with other VMs on the same hardware.