Actually, "Hey You, Get Off of My Cloud: Exploring Information Leakage in Third-Party Compute Clouds" (http://people.csail.mit.edu/tromer/papers/cloudsec.pdf ht

Actually, "Hey You, Get Off of My Cloud: Exploring Information Leakage in Third-Party Compute Clouds" (http://people.csail.mit.edu/tromer/papers/cloudsec.pdf http://people.csail.mit.edu/tromer/papers/cloudsec.pdf) documents "the tendency for EC2 to assign fresh instances to the same small set of machines", and exploits this tendency in order to co-locate a malicious instance with a victim instance. Rapid re-instantiation seems like a bad way to improve performance.