haha.

Sorry.

There's actually a site called FML.
People post [usually anonymously] about just horrible situations or things that happen to them or that they end up in.

It's pretty funny in a "this is terrible and humorous in a 'if I don't laugh I'll cry kind of way'".

And the people who post there are sharing because of that.
When I use it it's sort of in that spirit.

Or the "really? REALLY?"/ "you have to be kidding me" type way.