The ALA has the results to a survey done by by the Library Research Center of the University of Illinois at Urbana-Champaign on internet policies in public libraries. Some of the results seem a bit suprising.
-95 percent of public libraries have a formal policy in place to regulate public use of the Internet
-80 percent of respondents say they purposely locate computer terminals in open spaces
-64 percent of respondents require permission from parents before children can use the Internet
-Almost 50 percent have received informal complaints about Internet access, but only 7 percent were about content
A full report on this survey is available from the University of Illinois Graduate School of Library and Information Science at The University of Illinois (it\'s a pdf)