The post indicates that Facebook users who post this message will see their icon turn blue, and that Facebook will be free for them. The post even claims it was on the news. It is easy to see how users who do not follow the latest tech news could be tricked into believing a post like this, especially since it is coming from someone on their friends list.
Just remember this is a hoax, and it is not to be believed. Facebook has stated multiple times that it will never charge for their basic service, and that will continue going forward. If you see someone post this on their Facebook, be kind and let them know that it is not true, and there is no need to worry. The only way to stop hoaxes like this from spreading further is by letting people know that it is false, and their Facebook account will continue to be free.
I do not see what anyone has to gain from this. There are no links involved, so it seems as if it was started by someone strictly for a joke. Still, you can help stop the spread of the hoax by telling people not to repost it and by not doing so yourself.