Ittay Eyal and Emin Gun Sirer's discovery of the power of even a less-than-majority set of colluding parties to compromise the bitcoin ledger once again surfaced in the news.  This time, due to the planned bitcoin operation reduction of minting rate. This prompted concerns, bolstered by Eyal and Sirer's work, that already-influential parties could be better position to create disruptions.

http://www.coindesk.com/ahead-bitcoin-halving-51-attack-risks-reappear/