Authors John Scalzi and Seanan McGuire (both recent HUGO winners) provide some advice on the use of the “@” in twitter.
At Unbearable At-ness of “@”
“@”-ing someone’s Twitter name explicitly means that your comment will show up in their reply feed — i.e., that you’re directly letting them know you are discussing them. The basic gist of Seanan’s piece, as I understand it, is that “@”-ing someone is the same as inviting them to participate in the conversation; if you didn’t want to have them in the conversation, you shouldn’t have issued the invitation.”
“(I feel the same way when people title a blog post “An Open Letter to [Insert Name]” and then get huffy when [Insert Name] shows up or otherwise responds. Dude, what did you expect? You posted an open letter to them. Surely you understand that an open letter to some person is actually still a letter to that person? You don’t? Well, surprise! File that one under “words have actual meanings.”)”
http://whatever.scalzi.com/2013/10/09/at-unbearable-at-ness-of/
Seanan’s original post is here http://seanan-mcguire.livejournal.com/536270.html
If all this is sounds like ‘voodoo’ and you’d like to know more about this Twitter business Mashable has a good beginners guide.