[thomasbk]

The mining pools (groups of miners who've joined forces) control it in practice. This effectively gives a very small number of people control over significant things, like transaction fees.

[ensignavenger]

But if the managers of the mining pools were to do anything too overt, those who contribute computing power to them could (and probably would) quickly pull their support. At least in theory.

[thomasbk]

Those who contribute share in the profits of the pool! Most things that are in the interest of the pool are in the interest of the miners.

Also, as hardware gets more specialized, the cost to entry gets higher and power concentrates.

[jaibot]

This is also how fiat currency works. Which is all well and good.

[fnordfnordfnord]

But anyone can mine, so it would be difficult for miners to say, form a cartel and jack up transaction fees.

[thomasbk]

You can only mine (for a significant share) with very significant investments, and transaction fees competely go to miners, so it's in their interest to raise them (albeit slowly, to not curb the adoption of bitcoin too much.)