If you have a Facebook account, and get a message from someone saying "it is really you in this video?" or something similar, DON'T CLICK ON IT!!!
If you already have recently clicked on it, you have probably had your details stolen and your Facebook account has been hacked. The person it says it is from, didn't send it.
I've had this message twice in two days from people who also use this forum. If you recognise this message and did click on it, go and change your Facebook password ASAP.