Have noticed this lately - and ToadintheHole, I'm going to apologise straight off, because you've just done it to my name, but it's not an attack on you, it's been bugging me for days - lots of @username when addressing someone.
Now, I'm assuming that this has some technical necessity on Twitter (don't touch the stuff, myself), but what's wrong with just username, without the @. If you say my name, I know you're addressing me. I really do.