Useful tweets?

I subscribe to an e-newsletter from the site I Heart Technical Writing, which last week focused on how technical writers could use Twitter. When the newsletter arrived in my inbox I went to the twitter page and found some useful links (at least, I thought I did, but now that I look at it again, all I can see is lots of people getting excited about their 4 July celebrations). I also received an email last week from the Board of Editors in the Life Sciences, suggesting that freelance editors should add their twitter ID to their business cards. I’m not sure about the value of this, or the point of tweeting. I hope that someone can enlighten me.