To your first point, the vision is to use other Ethereum tokens tied to various assets and securities. How those asset-backed tokens are set up and how trustworthy they are depends on the individual token. I know there are a few asset-backed tokens (gold, real estate) but I have no knowledge as to how legit they all are.

To your second point, the collateralized loan allows for very very low interest margin investing. You can use the DAI to invest in something, sell it at a higher price, repay your loan, and make money on the difference.