While I agree that multi-tasking is a bad idea for productivity, three monitors don't necessarely lead to multi-tasking.

It really depends on how much screen space you need to efficiently do one task. Having three monitors myself, I mostly use two of them, sometimes one or sometimes all three, depending on the task. So you can still minify distraction.

And there are definately tasks where three monitors come in handy and save me a lot of window switching / aligning.