Today I went to a security talk and the speaker gave a demonstration of how when you tweet a link various “robots” will follow the link and index it and do other things.  He gave a couple of example of what could be done.  One example was tweeting links to login forms with valid user id but invalid password.  Since most login forms will lock the user out after some number of tries this will annoy users.  Especially since based on his research the links will be revisited long into the future.  So, the user may have to reset their password multiple times.  If you had all of the usernames one could lockout all of the users without anyone knowing it was you who did it.

He also was trying to actually figure out whether it was a human that actually attempted to load the link.  So, he discovered that different browsers have a certain cut off on the number of 403 redirects it will handle before quitting.  However, he has found that many bots will just continue to follow the redirects.

He also showed some other cool hacks.  The spring lunch group went out with a bang :)!