To be blunt, I have some problems with blogging and wikis for educational use.
I'll give some history to my own experience with blogs for perspective. I've had a personal online journal since the age of 12. That was 14 years ago. This was when Ask Jeeves was the height of sophisticated internet research. To give you some idea of what the internet was like 14 years ago take a look at this Huffington Post article:
What The Internet Looked Like In 1999
As shown in this article I used my-diary.org for several years and then eventually ended up on livejournal.com. I enjoyed blogging and journaling a lot. I was able to write down my thoughts and feelings without reservation. The problem with this was that these were public forums and that anyone would look at them. I learned at a very young age that the internet is not a friendly place. Online bullying is a huge concern for parents and should be a huge concern for educators. Although we try our hardest to make sure our kids conduct themselves in an appropriate manner there is always the chance that something they post online will be used by 'trolls' or classmates as fodder for ridicule.
Blogs are not regarded in the same manner as published journals. People are able to anonymously post comments directly to blogs and some wikis about the content of the entry. When covered with the mask of anonymity students feel they are prevented from harm or prosecution.
After reading some of the material given to us this week I can see what good that these resources can have for students I just worry about privacy.