Like a lot of you, my Facebook feed often fills up with dodgy adverts for discount sunglasses.
In this case, Mark's account has been hacked and the spammers are tagging lots of his friends. The post then shows up on my feed as "look what your friend is up to!"
Annoying. So, here's how to stop it. There's a slightly obscure FB privacy setting called: Review posts that friends tag you in before they appear on your Timeline?
Timeline Review controls whether you have to manually approve posts you're tagged in before they go on your timeline.
That means, you'll always be asked before people can tag you in a post. It's meant to be used so that people can't tag you in embarrassing photos - but it has the nifty side effect of stopping spammers posting their rubbish all over your friends' walls.
Visit https://www.facebook.com/settings?tab=timeline§ion=review&view and enable the setting to kill off the spam.
Tell your friends!