fell victim to this today: http://tw.help.cc.yahoo.com/help_cp.html?id=7224
Apparently the fix is here:
http://tw.m.wretch.yahoo.com/blog/icelove1221/13629340
Long story short - dont pass on authentication codes or call phone numbers you dont know at the behest of your "Friends on facebook" unless they will 1) tell you *exactly* what it is for or 2) they are with you in person...
:(