Sometimes, I ask a question on stack overflow, and then go to Twitter to see if I can get help there. Any developers that follow me are immediately directed to the SO question. I've actually seen a few devs sign up for SO because of this.
The steps I follow are this -
- Write question on Stack Overflow
- Shorten the URL for my newly posted question
- Think of a tweet that is 140 characters - the length of the url
- Post the tweet
It sure would be nice if there was a "Tweet this question" button on SO. Maybe I would push it, and then a tweet would be auto-populated for me using the tags - maybe one that says "Help me with this (tag1, tag2, tag3) question on stackoverflow" and then a shortened URL.
Although some of the answers already added are wary of a million "share" buttons being added, I don't think very many people use those sites as they use twitter. In a lot of ways it's as much a question answering service as SO is, and as I described above it's helped me find answers to programming questions.