Going back to the topic of Mystcraft griefing, there's several other things one can do which would be... naughty.
"We've secretly replaced your bookstand's book to your nether base with an idendically named one which transports you to the exact same area... sans gear"
"We've secretly replaced your bookstand's book to your nether base with an identically named one which transports you to a huge hollow hill in the Twilight Forest... sans gear, of course."
"We've set up an experiment to see how intelligent you are. Your bookstand's book was replaced with an identical looking one. Now you are to traverse this maze, naked, which was built in a Void Age. Should you find the correct exit, you shall be appropriately rewarded. Should you choose poorly, things will go... unwell for you". You could have a maze spanning a couple of void ages popping back and forth between each other. The 'correct' book will take him back to his home. Other destinations are... up to the creativity and innovativeness of the griefer.
Now, the lamerz greifer prank would be "We've replaced the floor where your book home drops you with a crystal portal that drops you in the nether approximately ten meters above a lava ocean in the nether. Enjoy!"