System administrators tend to be restrictive in installing new software.
Instructors may have difficulty in assessing student participation in the weblog. There are
several indicators to take into account: group grading, individual posting, quality of posts, etc., as well as subjectivity vs. qualitative appreciations.
If the weblog is public, it may suffer troll infestations, people that intentionally try to cause
disruption by posting messages that are inflammatory, insulting, incorrect, inaccurate, or offtopic, with the intent of provoking a reaction from others.