Songs About Twitter

Dear Rich: I'm a composer looking to set texts from blog/Facebook/Twitter posts. Probably 20-30 words from each post, woven together in a musical work. My question is are posts made on social media sites considered public domain? If not, does fair use come into play here since I'm using so few words from each post and weaving them together into a new and unique work? 
We think you should proceed with your project. Here are some rules to guide the process:
Short phrases are not protected under copyright. That's right, copyright does not protect short phrases. The trouble is that nobody is clear as to how "short"  a short phrase can be. We've written about "protectable brevity" before and as we pointed out, it's not the number of words taken, it's the uniqueness and value of the words as well as the way in which you re-use them. The risk meter generally goes up when you take more than about 20 words.
Fair use may work but ... Even if the posts are protected, your project sounds ideal for fair use protection -- that is borrowing short amounts of verbiage for purposes of commentary or transformative purposes. Of course, we must always point out that fair use is a defense that is raised after you're in a dispute.
Just Sayin' Dept. It's unlikely someone will sue over the use of a tweet or a 20-word Facebook entry but one individual who borrowed Tweets for her own artistic purposes suffered backlash in the marketplace. For the same reason you should avoid posting any tweets or posts that identify an individual and reveal personal information. It's unlikely someone can claim privacy concerns over a Facebook or Twitter post, but if you're seeking smooth sailing, you should avoid that sort of activity.
BTW Dept. There's exciting news for copyright geeks: The Copyright Office has unveiled a searchable fair use database. Check it out.