Mixed Economies

cutting staight to the point, what are the common problems associated with mixed economies?

As it all boils down to the extent of government control over the economy and other different factors, I can't seem to find a precise  answer my question.

"Private business interests always wants to deregulate the economy"

Not so much anymore, they just want a different brand of regulation. Many buisness owners now see the government as a tool to cheat and manipulate the market in ones favor. This action, if you ask me, is the pitfall of a mixed economy.