It educates by providing information about the attack used and how to prevent it happening in the future. You can find the link provided to users here: http://jonty.co.uk/idiocy-what

The tweet can be instantly removed by the user. It's hardly vandalism as nothing is being damaged or destroyed.

As I've said in a message elsewhere in this thread, posting to your own account is an easily understandable visible demonstration of what's possible and why they should care - a DM from another account, or an @ just won't have the same effect on the user.

I've been informed that it's possible to send a DM to yourself, so I'm going to add that as an option shortly.