Thanks.  I'm just wondering what kind of impact the number of nodes may have on the overall network reliability.
The power is currently about 50PH/s but this seems to be spread among 10K nodes only.  Is it correct that to shutdown bitcoin one would have to take 10K nodes down? by physically disconnecting, destroying them or banning their IPs?
Would the network be more reliable if the same power was provided by 100K, 1M+ nodes?