What about acting? Or fiction? These are artificial experiences that evoke real emotional responses. Once the right buttons in your brain are pushed, most of your brain can't tell the difference between what is real and what is synthetic.
Granted, authenticity in human interactions is important, but it's overrated. Fake engagement often is a perfectly acceptable substitute. Situations where people put considerable effort into *seeming* pleasant usually *are* more pleasant than they would be if everyone felt free to paste their indifference to you right on their faces.
So this is a very interesting technology. What's disturbing about it isn't that people might be fooled into thinking the user is truly interested; it's that the user himself no longer puts any effort into creating that illusion. What if that effort is in itself something important? What if fake engagement is often the prelude to real engagement? Maybe you have to start with polite interest and work your way up to the real thing; I suspect the dumber parts of your brain can't tell the difference. If that's true, taking the user's brain out of the interaction means that interaction will automatically be trapped on a superficial level. This already happens in bureaucratic situations where employees are reduce to rules-following automatons. Take the brain out of the equation and indifference follows.
I suspect that the researchers are well aware of these issues; I believe that I discern a certain deadpan, ironic puckishness on their part. People who truly view engagement with other people as an unwelcome burden don't work on technologies that mediate between people.