Maybe you don't need 13% stake to attack BitShares maybe you only need 0.13%...
As a proxy offer to pay 1% interest per month to accounts that proxy their stake to you. That would be a lucrative 12%+ p.a
1 months interest payments on 13% of proxied stake would only cost you 0.13%
Discussion continues over here:
https://bitsharestalk.org/index.php/topic,20724.msg267958.html#msg267958
Quote from: Empirical1.2 on December 23, 2015, 02:22:03 AM
As a proxy offer to pay 1% interest per month to accounts that proxy their stake to you. That would be a lucrative 12%+ p.a
But when the accounts see that you are attacking the network, they would pull their support and elect honest witnesses (maybe).