This a very dangerous plug in. It has the ability to delete not just what it creates, but every blog and user in your installation at the click of a button.
I cannot understand how any plug in has the ability to do that.
If it's purpose is merely to create demo data, then why program it to delete everything?
Especially when the delete is Titled "Delete Demo Data", yet it deletes EVERYTHING.
I do not recommend this plug in to anyone who has never used anything like it before and I definitely do not recommend it to novice users.