The calculation is fine. People buying premined currency already calculated this risk into the price of the coin. Thus the calculation is good.
Considering your close association with Auroracoin I can understand why you may feel this way.
The fact remain that 99% of the coins comprising Auroracoin's current "market cap" are in the premine and do not circulate. Should Bitcoins that have not yet been mined be included in BTC's market cap?
Cryptocurrencies aren't companies and coins held in an uncirculating premine are not issued shares. It might be worth making some adjustments in how market cap is calculated.
coinmarketcap.com loses much of its utility if market cap can be gamed by coins with a large uncirculating premine. Auroracoin is just the first coin of this type. Considering it's success, a wave of clones will come next.
Same shit for Ripple and his $1.5B market cap...
Ripple = decentralized exchange, XRP = centrally issued virtual asset/"math based currency" on Ripple. I guess you talk about the latter.
At least for Ripple I know that there could be a security breach at any moment at RippleLabs leading to a sale of all XRP they own. The only thing that pervents this is their security measures and their promise to distribute XRP fairly over time. This is not a part of the Ripple software, but something external to the network itself.
I don't know about Auroracoins, they too might already be stored on an address that is currently in escrow somewhere. As long as they have been created and could theoretically be moved, if the escrower(s) prooves to be dishonest this means they already exist, unlike e.g. the 20 millionth Bitcoin which has not yet been mined and even with huge efforts will not be mined (and thus made theoretically transferrable) for a very long time.
If they have not yet been created, I would remove them from the market cap. If they can be created easily by someone or already have been and are just depending on somebody to fulfil a promise and keep a private key secret, then they should be included, just like Bitcoins that have been mined but never moved are also included.
