Two common ones are:
1) One of your friends all of a sudden sends you a message that he needs emergency money because he got robbed or something in a far away land. You are then engaged in a conversation to wire him some money. This is what happens when your friend has somehow gotten his account taken over.
2) You receive a notification of a link about some video and you try to click it. Subsequent dialogs come up asking you to install something. Forget it. That’s very likely to be a virus or trojan horse. It’s not worth seeing the movie, especially, since you won’t. You’ll get your password stolen and the above scenario may happen to your friends who might actually care enough to send money thinking they’re saving your hide, and ask you for the $5000 when they see you the next time.