I work for Rackspace, we have a cloud. Sometimes people do illegitimate things with it -- but attackers using resources fall generally into two groups:
1) Fraudulent Payment method (eg, stollen credit card)
2) Someone hasn't patched Wordpress (or another app) in 3 years, box gets hacked, then used for bad things.
So, at least with paying via BTC for compute, you pretty much eliminate #1 -- in all cases the provider gets paid, no chargebacks, etc.