You put up a status update. You are so popular that there's an avalanche of comments, let's say from Tom, Harry and Sally. Then, in one comment, you have to reply to them all. So you go:
@Tom - Thanks!
@ Harry - You just don't get it, do you?
@ Sally - :)
@ Tom & Harry - Where's your friend these days?
If I am writing the names of the people I am replying to, then why the @?
Maybe I am just thick and not 'with it'. Or, Harry-like, I just don't 'get' it.