RE: Will Coinbase support Ethereum staking? If yes then Ethereum will easily become the most attractive asset to hold
I doubt Coinbase will pay interest for a few reasons:
Minimum amount to stake is 1,500 Eth, nearly USD-equivalent of $1 million. Folks with that much Ether probably can figure out how to stake it themselves or find someone besides a centralized, hackable exchange to do it.
Coinbase probably will not be permitted to "pool" Ether of many users to reach that 1,500 Eth threshold. Coinbase is a money transmitter already subject to strict state-based regulations, and they're looking to become an exchange subject to federal regulations. As a money transmitter, they would not be permitted to pool and pledge user funds.
"Unstaking" will take four months. "Stakers do not lose their money, but the ether used to stake will get locked, meaning that they cannot access it for around 130 days. After that, it can be freely used once again. This acts as a means of preventing people from fraudulently flooding the system and trying to damage it." https://cryptodisrupt.com/details-about-ethereums-huge-update-have-been-released/ Most won't want to lock their funds in a volatile crypto for four months given the risk of collapse.
And, this latter is the answer to the question you pose below, restated here: "So why would you have to ever sell the "principal" once you have enough of the "stock"?"
Because this "stock" is hugely volatile. In exchange for between 0% - 5% interest (very little), why would you agree to lock up your funds for four months, preventing you from selling when, say, it's discovered that there's a major flaw with sharding or Casper or another hard fork is imminent? That's why you don't stake and that's why you would sell the stock.
Where did you hear that the minimum is 1500 ETH? That could end up being any amount in USD so is this set in stone or dynamic? I haven't seen that number anywhere.
I also would not assume people with a lot of ETH have technical expertise. A lot of people can buy 1000+ ETH on Coinbase and not know how to launch a smart contract or deal with the very hard to use Ethereum Wallet. I would say this creates a market for pools and because these pools will for sure exist I do not see why Coinbase would not take advantage or form a partnership with one of these pools.
We will have to wait and see but if they don't then it's a huge loss of potential users who could then go to another exchange which does allow staking.
Follow the link in my initial post. The 1,500 Eth minimum is at many sites, including some that are direct quotes from Buterin, such as this one: https://www.ethnews.com/vitalik-buterins-five-steps-to-becoming-a-casper-validator (hint: read Step 3)
I didn't assume that all folks with Eth have technical expertise. Here's what I said: "Folks with that much Ether probably can figure out how to stake it themselves or find someone besides a centralized, hackable exchange to do it."
In terms of pools: Possibly. But, again, go back to my original post. Coinbase can't be a pool operator because they are a money transmitter and are forbidden from doing that. Someone not legally organized in the USA could. Coinbase can't. Plus, Coinbase wouldn't because they are attempting to become a licensed exchange. It would be like NASDAQ creating its own S&P 500 fund to sponsor. They can't do that.
I do agree the interest levels are crappy considering the amount of risk but if someone is going to hold anyway there is a penalty for holding. Meaning if you don't stake you are guaranteed to lose some percentage of your value each year in terms of percentage of Ethers.