demo.acumatica.com does not exist anymore although it was very handy. I understand that people can mess it up badly but, one can just reload the demo data, or simply disable any editing. Just reloading the demo database weekly using a script is preferred.
Quick access is is very very useful especially when you meet somebody at a seminar, and the person just wants to have a quick look at Acumatica.
Besides all the negatives about demo.acumatica.com , I think that the positives outweigh the negatives.