We've updated the backend to provide more fair sharing of CPU specifically to account for cases of mining.
Luckily the high value of Bitcoin has drastically dropped in the last 6 months and we've seen this reflected in a much smaller number of active users mining bitcoins.
Much of the mining was happening by fraudulent accounts as the economics of mining bitcoins or other cryptocurrencies weren't financially feasible when there are server farms based on GPU systems that were driving the valuation along with the overall speculation in the marketplace.
Hopefully customers have seen a reduction in the amount of steal time as a result and if you are still seeing a high percentage of that please open a ticket and we'll review the hypervisor in question to see if there are any abusive accounts that need to be addressed.
Thanks very much for the feedback!