As i have said earlier, this is really important, and i believe it must be changed at the shortest time.
I just forgot to change the instance name today, making a new subdomain install, and i werent able to log in of course; I know that i have to change my instance name to sth unique, but thats only because i am a regular b2 user.The new users wont know they have to change it so that they wont have problems.

Just create a random instance name upon install or at least propose the user to enter one during install