I'm not sure whether to take you seriously or not. I would have thought the difference between a simulacra and a real human was obvious. Real human performers react to the audience. Real performances are two way communication. When did the 'youts' of America start believing that computers and real life were interchangeable?
They aren't interchangeable. However, unless its some small, local band, you don't get more communication with a real singer than with a fake one. Most communication is set up in advanced anyway. I.E. audience sings a big line in the chorus, etc.
At the end of this concert, you will have as much of a relationship with the holographic singer that you will with a real singer. It is very much like a laser light show, as somebody else said. It is just entertainment, so why does it matter in what form (human or otherwise) the entertainment comes in? Anyone who believes the somehow have a relationship with a performer after a concert is delusional.
Take it this way. If they replaced a real singer at a concert with an ultra realistic robot, you wouldn't know the difference and it wouldn't matter to you. Why? You don't know that person and you never will. You aren't intimate with the person. They aren't your friend. Therefore, it doesn't matter if they are even real. They are just entertainment in the purest form.
EDIT: Most of you guys don't understand that this concert is more of a celebration of community than a celebration over the artificial singer. A whole community drives the vocaloid phenomenon, and by going to this concert you feel closer to the community and can *gasp* make actual friendships with others.