Wikis, social bookmarking and the class room

I do believe that wikis and blogs are incredibly useful tools but I am unsure of how useful they are in the classroom. Because these sites are open to editing by everyone I feel this can only increase the amount of false information that is presented as fact. Blogs might be an interesting way to engage a student to write but again I can see how this could be misused by both the student writer and those reading it. I have been informed also that school districts are starting to have some very strict rules with regards to teachers using such sites. So I am unsure as to how much if any I will use these resources.
I am a big fan of bookmarking and find it very helpful but have not used social bookmarking. I can see how social booking marking could help keep your class on the same page. You could also use it to direct your students to information that could be useful to a lesson. It could serve as a great extension of what you are teaching in the classroom.
I have used tapped in but, in all honesty, I find it to be somewhat confusing and not well laid out. It is, for me, a case of way to much information and not enough time or patients to track down what I am interested in. I belong to a couple of other teacher networks that I find more helpful.

References:

Jonassen, DJ, Howland, JH, Marra, RM, & Crismond, DC (2008). Meaningful Learning with Technology. Upper Saddle River, New Jersey: Pearson.