I am a big fan of Twitter because it's basic infrastructure that people can choose to use in whatever way suits them. I use it as a conduit to update those twits that follow me, to update my journal sidebar, and to update my Facebook status. I can update easily from anywhere in the world where I have access to SMS. I have phone notification via SMS turned on for only a very select group of people -- a small subset even of those that I "follow." However, it seems that anyone out there can direct message me in Twitter -- even folks that I do not even follow... and these tweets use the "phone notification" master privacy setting, which has to be "on" if you want SMS delivery at all. This is a completely flawed approach. There should be an additional setting that says something like: "Only notify direct messages from people I follow" or "Never notify from people I do not follow."
At the moment, I get lots of direct messages from Twitter users I have never heard of. These go direct to my phone as SMS messages. I don't really want to get advice SMS'ed to my phone from strangers.
Here's a typical exchange:
Eric: [complains about something. makes veiled cry for help.] Stranger: @echeng omg lol you need to take it easy!
I see that reply as being totally intrusive, even if the stranger didn't mean for it to be taken that way. The problem isn't the stranger; it's Twitter's lack of sophisticated privacy settings.
I've submitted feedback to Twitter about this. They said, "good idea!"
I hope it gets implemented soon.
If you don't "get" Twitter, don't worry -- I won't try to convince you to use it. But the stats speak for themselves: most people I've convinced to give it a try are still using it.