In addition to the problem of maintaining community when the number of people increases, I also think that it’s a function of communicating in writing, rather than in person.
I vaguely recall attempts at quantifying the loss of information when communicating in writing due to the loss of tone of voice and body language. i.e. even if your words are rough, your tone of voice and body language may allow you to be better perceived.
In addition, the increased likelihood of participants writing in something other than their first language, increases the chance of misfired communication significantly.