Hi Patrick,
I came across
this blog post that I feel is a succinct summary of the different thoughts on this. The comments are especially interesting. As far as your specific example of the librarian reaching out to teens, that seems to be the easiest one to try out the blur between professional and personal--because teens don't see a separation and in fact may expect/appreciate seeing the "whole person" behind the communication. It may be less appropriate for other patrons who are less comfortable with that. It also seems to me that organizations who are leery about allowing staff to do this should articulate their reservations with staff and see if they can work together to put together some groundrules about what is unacceptable behavior or content on a staff profile that is ever used for business purposes.
Sharon
