The use of @ to tag somebody in a message

Hi,

BTW, did you notice that in Geni, we can tag somebody in a message like the following example:

My 3rd brother's name is Private User. Whereas in the facebook should also has this sort of feature, but I don't see that it works in facebook!

Eddy

And, hey Private User, Elin Kwok, Yon Kwok, Rudi, what do you think of this?

Eddy,

Let me try a tag tips from you, my youngest brother is Eddy Kwok
Thanks for the tips!
Cheers
Antong