'Imagine walking into a party where everybody is wearing wireless headphones and is singing and dancing to an inaudible beat. This was the vision of the founders and creators of the Silent Disco' (more here)
Hmmm... it's one thing people dancing with headphones at a flashmob style event, but I am deeply sceptical about silent club nights , with people paying good money to wear headphones (the above quote is from an article about a Silent Disco night in Bath next month) - even if they are listening to a mix broadcast to them by the DJ rather than to their own individual soundtrack.
The problem is that even if people are dancing in synchrony to the same music (see Global Raver's criticism of iPod raves), the common soundtrack is only part of the collective experience of dancing - even in the loudest club there is generally the possibility of some kind of conversation, something that is presumably not possible while listening to music on headphones.
In addition what goes in through the ears is only part of how we sense music. Dance music in particular entails feeling the bass in different parts of our bodies. I really noticed the absence of this last year when I saw Kode 9 DJing in what is usually an indie pub in New Cross (Amersham Arms) - playing through a bass-lite sound system set up for bands, it felt like a key part of the music was missing. With headphones even more of the music must be missing - you just cannot generate the same bass sensation through the ears alone.
Of course I've nothing against the Silent Disco people, I'm sure it's fun as a novelty. My real concern is that it might pave the way for the future with 'noise pollution' being used as an excuse to require clubs to replace speakers with headphones. That really would be the end.