One Amazon "EC2 compute unit" is, according to them, approximately equal to a 1ghz 2007 Xeon processor (that's a m1.small).
Judging by my laptop generating experience, there's no way an m1.small instance would generate enough ฿ to be profitable.
The heftiest instance you can buy ("large CPU") is 20 units big, and costs $0.231 per hour; with bitcoins selling for about a half a penny each it would have to generate 46 per hour (or about a block an hour) to break even. Ummm.... no, that does not compute.
RE: how did I get hashes-per-second on my mac: I applied laszlo's patch to a version I compiled from source code.