[sien]

That's pretty much The Lump of Labour Fallacy:

http://en.wikipedia.org/wiki/Lump_of_labour_fallacy

Your comment applies not just to robots but to any labour saving device or productivity increase. From the wikipedia page:

Historically, the gigantic increase in labour productivity induced by technological progress since the industrial revolution has resulted in the dominance of the scale effect, bringing about both a massive increase in real wages and a decrease in labour time. There is no reason to expect that this same process cannot be continued in the future.