Walmart isn't known for being a great place to work. If people can live at minimum without having to work, Walmart can kiss its artificially cheap workforce goodbye.
I think a significant result of these sort of minimum income ideas would be an explosion in the amount of people that opt for risky entrepreneurial ventures (eg. a startup) instead of working bad jobs for the basic necessities. I think many people would rather make art or pursue other risky, generally low income, creative careers than do low skill, uninteresting work.
A result could be that companies offering low skill, minimum wage jobs could have to raise wages or improve their jobs in other ways in order to attract workers.
Automation is not a new thing. Imagine if the people who built the pyramids had trucks.
There was a commenter on HN who said once: "When cars replaced carriages, did the horses get new jobs?"