This is incorrect, a friend of mine was playing with someone, both using the exact same DNAS ID, neither of them were banned.
At this point it isn't established as far as I know whether DNAS IDs are 100% unique or not, as there are instances where 2 copies of the same game have different IDs. Whether this means that IDs are unique to batches rather than each disk, I don't know. Theres also a theory that the ID is generated uniquely based on the console, so sticking the same disk in 2 consoles may yeild a different ID each time. This could be easily tested I guess...
Sony may be banning IDs posted on the internet, but as far as I know they aren't banning people who connect with the same ID at once.