If you mod a comm and see a post claiming outrageous news and linking to tinyurl, please delete that post as soon as you can. JKR did not die, the world is not ending tomorrow, and your grandmother is fine too.
In general, before you click any link, ever, make a habit of looking in your status bar to see where the link leads. If it's a cloaking service like tinyurl or any of these, feed it to the w3c Validator first to see what link it's obscuring.
Pass it on.
p.s. Also, see here and here for more information about the recent account break-ins.
p.p.s. communities affected thus far: deamus, hp_ot3, harry_and_ron (sorted!) -- one of the maintainer/mod accounts has been taken over.
...though in the case of deamus and hp_ot3, notifying would be pretty useless, since the other maintainer appears to be in league with whoever's doing this. :\