One thing that this article misses about twitter is that you carry your followers around with you. So if you have 1000 followers and you tweet at someone, whatever you're saying, you're saying in front of 1000 of your fans. So if you disagree with someone not only are they going to get your criticism, they're likely to get 1000 people piling on behind you. There are lots of things I can say to you one on one that are suddenly basically bullying if I've got a mob behind me.

Equally, if you draw attention to someone, even if you aren't disagreeing with them, you have to be aware that you're likely subjecting them to a level of unwanted attention from your audience.