You can make a coin on Etheruem usually referred to as a meta-coin. You can also make a meta-coin on bitcoin.
Ethereum is switching to PoS, then people will be able to clone the network and 100% premine it if they want. PoS is the interest for having the wallet open thing. I would recommend Synereo over Ethereum if you want to do something more serious than write a few smart contracts that'll break later on due to a bug.
Thanks for your comment. Yes PoS coins are interesting and the way to go for a truly decentralized coin. I will give Synereo a look.
Thanks.