I think it's fine to keep markets in an economy to take advantage of market forces in certain consumer industries, but things like healthcare, natural resources, infrastructure (incl. the internet and the new internet infrastructure like Google & YouTube), banks, among other things should be nationalized. Markets (not unadulterated capitalism) can be useful in certain fields but it's foolish to use ruthless competition as the basis for production and distribution of resources.

History has shown time and time again a cycle of rising inequality, reactionary regulation, and a dismantling of those regulations. The depression, the downturn of the 70s and 80s, the recession in 2008... and that's just in America.