I've noticed a similar thing happen on various forums that I belong to. A happy group of people will have been posting messages - helping out, sharing information, the odd bit of banter etc. Then along comes a newcomer, who has to chip in with a comment or answer about every message, who is insensitive to the mood of a thread or particular person, and worse still, wants to press their opinion on everyone, becoming argumentative if it is not accepted. Like the music session, people move along - they stop posting and find somewhere else to go. What once was just a group of people who probably only knew each other by user names but gelled like a family, gradually begins to disintegrate and it may become worthless.
Thats the power of one.