Last year an old friend's Facebook got hacked. The hacker sent out a message saying my pal was stuck in London, needed money etc.
The grammar in the message was bad, I didn't think my pal was in London and I wondered why he didn't call his parents who have plenty of money. I actually saw that "he" (i.e. the hacker) was on Facebook as my friend and asked a couple of questions -- the hacker got pissy and I figured out it was a scam.
Just now I got a similar message from an old student. She got mugged in London, send money here etc.. This time I knew it was a scam because her grammar was too good -- and the message too calm sounding. Clearly, it wasn't written by my student -- who couldn't write her way out of a paper bag and was ALWAYS uber-excited.