Recently I was happy to have found David Lee King's blog about libraries and web technology. There are a lot of good conversations going on over there - most recently about Twitter and libraries friending patterns, plus a follow up where I perhaps waxed too rhapsodic in the comments.
He talks about libraries just friending other libraries rather than reaching out to their community. I added to that my experience of being friended by lots of libraries and librarians spread all over the country. Perhaps it's a unique scenario, since I use Twitter purely as a means of staying in touch with friends, but I did put that I was a library school student in my profile. And for a while, I was accepting all the friend requests that I recieved from librarians, so long as we seemed to have something in common in addition to that (usually knitting).
But eventually I let almost all of them go - they weren't twittering about things that interested me, and I had a really hard time imagining they were interested in the fact that my cats can be annoying, or that I love my crockpot. As far as library institutions go... if I don't have some sort of connection to them, I'm not sure why I would want to follow them. Besides, many of them don't pass the following/follower ratio rule (if there are a large number of people who you follow who don't follow you in return, I am probably not interested, either). I do follow places that I have some connection with - SF BART, for example. If the library in my neighborhood had a Twitter feed, I would follow it. But just because someone, somewhere has some connection to library science is not enough for me. Not for the way I choose to use the tool.
Which is not to say I don't wish my fellow library-related people and institutions well. I do. I just don't necessarily want to read about all of them every day. Life is too short, and time too precious.