@creighto
Asserting logic does not make your argument logical. Every miner has a cost to generate a block at a certain difficulty, if this cost is more than 25BTC+fees they would be taking a loss after halving the reward. There is nothing that says that at least half the miners have costs less than that. You just make that claim, asserting that it somehow logically follows, without explaining your logic.

@ribuck
Price of BTC also went up a lot, increasing profit margins and drawing investment into hashing power. Halving the reward is indeed like increasing the difficulty by 100%, without having been driven there by market forces, but because it was time to do it.

It will probably sort itself out in the end, but the sorting out process could be very painful I'm afraid.

I think the main problem is the 2016 block retarget interval, which IMO is way too long.
The difficulty could possibly be halved at the same time as reward halves, but this alone would just cause blocks to be spit out twice the speed for a week with a 100% rise in difficulty and back to square one after that. (Simplified example assuming no changes in market conditions...)

My point is, that I would like to see difficulty track actual hash rate a lot closer, and I think this would mitigate potential problems coming from reward halving or big drops in the price of BTC.