At risk of repeating stuff already expressed here because I haven't got time to read everything…
Bitcoin is one implementation of Blockchain technology
Blockchain itself has immense value and will be disruptive to many industries. The value is the ability to guarantee transaction authenticity as copies of the data are decentralized, to change a stored value means hacking many nodes of the network at the same time which is practically impossible. How will blockchain be disruptive? in commerce when a deal is done, the deal information can be stored in the blockchain and as mentioned distributed, for example, recording royalty payment agreements, bank transactions, anything of commercial worth where the integrity of the data and guaranteed accurate point in time reconstruction is required
Companies will pay to have a guaranteed audit trail for their data – retention periods for bank transactions are typically 7 to 10 years for example, and implementing local audit of business data on IT systems is a real headache – I happen to be working on this for an Investment Bank right now…
Personally I am avoiding Bitcoins – and I am not offering this as advice – because it's relatively easy to set up your own Bitcoin and do an Initial Coin Offering (ICO) to float a company using your own crypto currency. There is no regulation for Bitcoin so in practice one could set up a company, issue an ICO, retire on the proceeds, day trade against your own Bitcoin and have no legal obligation or regulatory imperative to run the company so floated. IMHO dishonest and abusive, but perfectly legal, and I know of someone who has done just that…