The Difference Between a Blog and a Wiki

Blogs and Wikis both seem to be good for sharing information. I can see blogs being useful for discussions or one person shows. Possibly a problem being stated and then folks involved contributing possible solutions. A committee discussing or conducting a project. I could also see it being useful for one person updating people at a time. I've seen this more in social situations for trips or new babies or family news, but it could also be applied to some business purposes. The main strength I'm seeing with wiki's is for multiple people working a one document at the same time and not having the horror of everyone making different changes and then compiling them to find out that many cancel each other out, etc. It also seems that wikis are better suited to organizing final content--but that might just be my not knowing them well enough yet.