I have been using twitter to grow my reach and network. I have close to 90 (mostly) quality followers now, and I tweet 4 ~ 6 times a day with BufferApp.
I'm mostly posting niche (small business, entrepreneurship, marketing) related content and then doing some interaction by answering niche related questions and interacting with my own followers.
I get a 2% ctr, but it is very content specific. One tweet might get 15% ctr, and the next 7 will get bupkis.
This is good though, because I can start to see what content gets retweets and speaks to my audience, and what doesn't.
Twitter seems to me to be a fairly new platform, a lot of people don't know how to use it, and a lot of people don't check it regularly, so I really see this as being able to make relationships with the 1% that do get social networking, so that when this is more pervasive, I have a foothold.
I think twitter for the original purpose which Jack Dorsey came up with, which was status notifications for services, is pretty cool. But selling, it's not there yet. There is too much noise and not enough genuine interactivity.
I have similar feelings about Quora.