Quote from: btcinsight on December 02, 2017, 10:41:17 AM

Cryptocurrencies marketcaps combined are now around 330 Billion USD, which is roughly 7.5% of cash in circulation in Euro and Dollars combined (around 2500 Bn USD)

Dollar cash in circulation was 1154 Bn USD in 2016:
https://www.federalreserve.gov/paymentsystems/coin_currcircvalue.htm

Euro cash circulation was 1143 Bn EUR in September 2017:
https://www.ecb.europa.eu/stats/policy_and_exchange_rates/banknotes+coins/circulation/html/index.en.html

Clearly, cryptocurrencies usage, apart from pure speculation, is way less than 13% of cash. Isn't it the sign that we are in a giant bubble?

Kind of. Currently, there are A LOT of people investing in cryptocurrencies, purely because they think they'll become rich if they do so. Therefore, they aren't using the Cryptocurrencies for what they were made for.
Of course, there are a lot of people that do actually use Cryptocurrencies for what they were made for, but the vast majority doesn't. And with a good reason: They're so volatile that they're not yet very useful for that.

Even on Bitcointalk, a Bitcoin/Cryptocurrency-based forum, there is a significant percentage of people who doesn't even know the actual concept of Cryptocurrencies.
When I look around the forum, I see that most only understand the concept of "Less supply, higher price, so let's invest in cryptocurrencies". Some a bit more, but Bitcoin got its popularity through that.

In short: Yes, we're in a bubble. It's going to collapse, but no one knows when. It could just as well go on for a couple more years, growing to unimaginable heights, if people are patient enough to hold their Bitcoins. One thing is certain: It will fall!