It seems like there are many challenges to offering customers reference via text. How do you have a cell phone number that everyone can check? How can staff constantly monitor text messages? And of course we can forget the issues of money and time (or lack thereof).
The Southeastern Louisiana University Library may have found a solution to at least some of these problems. Check out the following link from the "ALA Tech Source Blog" about the way this library implemented text messaging for students. http://www.techsource.ala.org/blog/2007/06/can-u-txt-the-lbry.html
Of course before implementing anything like this, you need to think about whether or not your customers will want this service. However more and more people (especially young people) are texting these days. Why not give them another way to reach the library?