There's nothing accidental about being in public when you're at a table at the mall, either, and yet we accept that people make communications in such spaces, which because of the medium carry beyond their party, that were really only meant for their group. In the same sense that voices carry in a public space, Tweets can be seen by a larger group than was intended.
It's a sad state of affairs if our only option for having semi-open communications on the internet - things that friends of friends can see without having to sign up to a walled garden - is if we only say things that are acceptable to everyone possible, for fear of mobs semi-randomly forming, or worse, forming at the behest of a for-profit company driving the mob in a frenzy to get ad revenue (which is the case for times companies like Gawker have stirred the mob up).
It's a sad state of affairs if our only option for having semi-open communications on the internet - things that friends of friends can see without having to sign up to a walled garden - is if we only say things that are acceptable to everyone possible, for fear of mobs semi-randomly forming, or worse, forming at the behest of a for-profit company driving the mob in a frenzy to get ad revenue (which is the case for times companies like Gawker have stirred the mob up).