It's not just mining. The general trend over time is centralisation of everything. That's because professionalism is important but takes a lot of work, and the most obvious way to fund it is through offering services and charging a fee. Right now for a lot of Bitcoin users, their experience is like:
- Buy some coins on coinbase (essentially a bitcoin bank)
- Send them to a friend who uses blockchain.info
- Mine on a big pool like BTC Guild or GHash.io
- From time to time, buy things from a merchant who is using BitPay
It varies by region of course. Here in Europe I see a lot of people using the Android SPV wallet, so that's at least fairly decentralised. But it takes huge and constant effort to keep the decentralised solutions competitive with the more centralised forms. Cracking that problem is something I've spent a lot of time thinking about.
- Buy some coins on coinbase (essentially a bitcoin bank)Personally, I feel the exchanges are becoming more decentralised over time, - last year MTGox was all powerful, now there are 4/5 with a big market share. - I think cheap and mobile Bitcoin vending machines will also explode this year. - I also think China & India are also inadvertently helping Bitcoin to become more decentralised by encouraging P2P exchange methods.
- Send them to a friend using blockchain.infoI guess a wallet/address can be moved anywhere if blockchain.info is compromised? As long as some smart guys are being vigilant of blockchain.info code changes. Maybe a document that explains clearly to non tech people (like me) how to move their wallet and gain control and security of their coins after a blockchain.info attack as quickly and simply as possible could be good though.
- From time to time, buy things from a merchant who is using BitPayYes this is centralised for the moment. But it is attracting thousands of new merchants to Bitcoin and thereby decentralising Bitcoin even more.
So whenever Bitpay is shut down, they will leave a legacy of hundreds of thousands of merchants who now have Bitcoin experience & the ability to transact in Bitcoin without them.
So IMO, though there are 'targets' for the nefarious in each of those areas you mentioned, only the ability to control large amounts of hashing power for an extended period has the ability to destroy the security & trust in Bitcoin itself.