Take for example DAI. It's pegged to the price of the US dollar, but it's collateral is stored in Ethereum. If the price of Ethereum were to somehow bottom out, to where the total value of the ETH in the collateral pool were less than the total value of DAI at $1 USD, the price of DAI would fall as a result of not having the liquidity behind it. If the price of ETH were to double up, the price of DAI would still stay pegged in at $1 USD.

I like that term elastic coins a lot more than calling the stablecoins, I've never heard it before now. I'll definitely start using it! They are more unstable that other stablecoins, but with the rebasing, they are also more stable than most other cryptos, so fall somewhere in the middle, and I think that elastic coins term is a perfect fit!