> It is economically speaking rational, to automate the bulk of the (middle income) jobs, as there lie the most potential savings. So without regulation this trend will continue (it will on the other hand continue even with regulation, I believe).

Is it automation, or is it more competition from other humans? In 50 years, the population of the US almost doubled. In addition, many workers (in most countries, not just the US) now have to compete globally (indirectly, if not directly) with equivalent people from other countries with lower standards of living. Both these phenomena can have negative effects on employment and salaries, IMHO.