Overview of the current state of mining

As of early 2016, mining is on its way to become more centralized. Mining equipment manufacturers are increasingly mining for themselves and not selling the hardware to consumers. Some of the bigger manufacturers now command 15% or more of the network's total hashing power. Recently, there has been a big run up of the hashing power. In the span of about a month, the hashrate jumped from 500 to 750 peta-hashes. In January 2016 it reached one exahash, and currently (Feb 2016) it is around 1.3 exahashes. (see https://blockchain.info/charts/hash-rate for up to date information).