Amazing analogy from Glenn Hutchins, from a meeting Oon January 14, 2016, where Brookings convened a roundtable technical discussions about the future of distributed ledger technology with industry and policy stakeholders.
A better analogy for Bitcoin is Copper, Copper has value but the main use for copper is to transfer power (or carry something). This is just like bitcoin.
Like joshia- says:
The copper analogy is one that will stick--it is the best analogy I've heard for BTC.
Copper's value is derived from its utility, as well as speculation--similarly to bitcoin. Essentially, copper is to wiring what bitcoin is/can be to payments.