With the installation of our new content filter recently, teachers and students noticed a significant increase in blocked websites. Overall, this has been (as might be expected), well-received by faculty and generally to the chagrin of students. One site newly picked up by the filters is Craigslist, an admittedly very useful place to purchase an awful lot of stuff. Some of this "stuff" can have educational value: computers, software, books, gym equipment, tools, etc., can all be had very cheaply for anyone willing to look for deals.
However, as one of my teachers exclaimed as I explained why he could no longer access the site, "Oh yeah, you can get hookers there!" Some of the "stuff" on Craigslist definitely bumps into CIPA concerns, so it will be staying on the blocked list.
YouTube, on the other hand, despite a fair amount of potentially objectionable content, remains unblocked at the request of teachers. There is simply so much good content that teachers are willing to police their classes much more heavily to ensure that we can maintain access.
In addition to YouTube, I stumbled upon a list of solid documentary sites online that provide additional resources for teachers. The list is hosted at makeuseof.com and includes PBS Frontline and Nova. Of course, it also includes Joost, but the point remains that several other sites exist that provide free lessons and supplemental materials for students. Add in such resources as MIT's Open Courseware and we just might be able to curtail YouTube usage in the coming months.