When i saw coolness factor for second i was thinking it would be coin that would lower heating necessary for mining.
Well, it's sort of more friendly. With Bitcoin, nothing is happening except heat is being produced. The calculations used for mining are completely worthless for general computing, and the rigs used for mining can't even be repurposed to do anything else (except break certain hash schemes, I suppose.)
Sia on the other hand uses its 'protection' algorithm to produce storage that is available to the general public. So while it's not 'free' in the same sense that a POS (how do we distinguish between proof-of-storage and proof-of-stake?) currency doesn't burn energy, Sia does replace the general datacenter, providing two functions at once. Overall I think Sia would be better for the ecosystem. But the other benefit is economic, because storage on Sia can only be acquired using Siacoins, which causes inherent demand for the Siacoin that's directly related to the value of the storage on Sia.
< this isn't strictly true... Sia relies heavily on fully random numbers, which ends up being very difficult to pull off in a quorum, potentially impossible. The solution we've chosen is a proof-of-work model (and actually, you can just use the existing Bitcoin blockchain), which damages the environmental argument because our random number generation is just as wasteful as traditional POW currencies >
Still I don't understand why both SCN and STK when it could be easily one.
What is unclear? Did you read the economic model?
Siacoin is supposed to be inflationary, because we want to keep the emphasis of the value on the people who are actively contributing to Sia. With Bitcoin, people who provided $1000 worth of mining in the first 6 months have hundreds of thousands of dollars of reward today. Imagine if instead that hundreds of thousands of dollars was going to todays miners. The hashrate would be higher, and the currency would probably also be more stable ("more stable", though I doubt stable enough to defeat the instability argument).
At the same time, we need a way to feed ourselves. At this stage, that meant doing fundraising, which meant we needed some convincing source of value for our investors. Selling a coin that's permanently inflationary didn't sound too attractive to me. The other thing is that I've always felt like premining is a "dirty" way to get money for the developers. It's not clear exactly how much value the developers will have, and there's a large potential for the early adopters to have control over the markets. Someone owning 1% of a currency can perform massive manipulations, and if they're good at manipulating the market they will profit greatly at everyone else's expense.
Siastock derives its value from Siacoin, but the reverse is not true. If someone performs a massive pump-and-dump on Siastock, only Siastock holders will be affected. This rests well with me, because Siastock is designed to be highly speculative. It's where the greatest opportunity for making money is. But it shelters the people who just want to use Sia for storage, as they will be using exclusively Siacoin. Over time (after the initial explosive growth of Sia... [fingers crossed]), the Siacoin should be stable in an inflationary direction, and ultimately a poor long term investment. Siastock on the other hand gains value as Sia gains value, and is a fantastic investment (though risky) for anyone who's confident that Sia as a whole will continue to gain value.
I think that separating Siacoin from Siastock will end up being one of the defining improvements of Sia over other cryptocurrencies.
