'Bubbles' are not economic phenomena like inflation, unemployment, demand and supply, income and expenditure, etc. There is no standard way of measuring bubbles, and, as far as I am aware, no standard model you could apply to e.g. 'dot.com' stocks, Irish property prices, tulips, uranium, etc. when they exhibit extreme price movements to determine ex ante if they are in 'bubble territory'. Just because you have an extreme price movement does not mean an asset is in bubble territory, as, in the real world, returns are not normally distributed. Also, in the aftermath of bubbles, the 'explanation' is usually of a non-economic nature, e.g. the banks 'lost control of themselves', market participants exhibited ' irrational exuberence', there was a lack of alternative investment opportunities, etc. If this were the case, i.e. if there were a standard explanation for what causes price bubbles, bubbles could be controlled but each bubble just gets its own ex post facto explanation. So I think bubbles are really pricing, or more correctly, mispricing phenomena. Also, not all extreme price moveemtns are regarded as bubbles. Recently a painting by Mary Swanzy, 'The Storm', sold for 100,000 EUR, despite a guide price of 25,000 EUR, but nobody suggested this was the start of a potential bubble in modern Irish art.
Before looking at the price of Bitcoin, I think a rational investor would look at his / her current portfolio to determine if (a) Bitcoin is an asset class and if so, (b) does it provide a diversification benefit, or (c) lower overall portfolio risk. I doubt Bitcoin is an asset class, as it does not represent a claim on future returns of a productive asset, i.e there are no Bitcoin earnings, dividends, roll yields, etc. At present, I think it's more like investing in paintings - there is no income return, you are betting on a bigger fool to buy them from you, and there is little or no diversification effect. So why would you buy them and not e.g. a painting, which at least you can look at, show off to your friends, etc.?
So I think Mr Burgess is correct. Bitcoin has at no intrinsic value, only price, but is it expensive? The only value Bitcoin has, at present, is the price others place on it. As the price is volatile it's a poor store of value. It's not a widely accepted medium of exchange (unless you are buying illegal things). Next year Bitcoin futures will be available, but against what are you hedging? It's very difficult to see this as anything other than speculation.
As for investing in blockchain technology itself, it's basically a chunk of asymetric cryptography. Baltimore Technologies were experts in this and they are not around today.