- miners: they bear the biggest costs and are responsible for the security of the network. Without miners there would be no bitcoin.
- economic nodes: nodes that have real activity going through them that relay transactions and accept or reject blocks that miners provide them. Coinbase's nodes are significantly more valuable than my personal node for my wallet.
- core dev team: their power is soft but integral, no-one wants a chain that can't be updated over time.
Owners of coins currently have little to no influence.