In my very first introduction to the concept of brainstorming, the class was instructed in the basic rule - no criticism of any idea no matter how ludicrous. The rationale being that one idea will spark another and the cascade effect in a group of people would have the most obscure trigger paths imaginable - but that somewhere in the midst of all the lunacy, a priceless gem could materialize. (Being scribe in these sessions was most stressful.)
Once the session was over, the list of ideas was then reviewed and assessed, with the absurd ones being duly acknowledged and dismissed.
I my first experience, the class was given the task of listing ideas for seating and I remember one of the ideas thrown up was 'ropes' - but I don't recall it making the short list afterwards.
However, with the eBay 'Negativity Chair', I have this vision of the 'ropes' idea being taken up with joy - because you can't be negative about ideas - and made to 'work'. I have no difficulty in believing the end product will be technologically innovative - but whether it services the real need of the end user is the correct question to ask.
I can see the eBay team taking the 'ropes' idea and turning into a noose, where they describe how brilliantly is was conceived and how wonderful it looks - with the presentation team making a big deal of how they explored multiple alternatives to tuck in the end, so it looked neat. You know the old saying "Tying up loose ends"!!
The only thing is that it would be totally useless in achieving the objective - and, mores the pity, they would probably be hard pressed to understand how to use a noose properly...
... and that's a shame in itself.
PS after working some decades in application development, I can honestly say that, from my experience, any serious IT person would cringe at the idea of stepping up and spouting off as these people have. These guys have either had a gun to their head, been brainwashed or lobotomised (before or after implementation is the question).
The only time anybody would do such a thing is in an internal training session for support staff - and even then they'd be feeling vulnerable.