What are the differences between a blog and a forum?

The significant difference is about "the agenda setting".

A blog is a "personal" space where the author controls the agenda.

A forum is a "public" space (sometime with restricted access) where the participants, with the help of a moderator, control the agenda (within the limits of the forum's topic).

• In a blog, the author(or author's thoughs) is in the main focus. In a forum, the topic is in the main focus.
• One reads a blog to know the author's point of view . One reads a forum to know the debate surrounding a topic.
• In a blog, the author is the authority. In a forum, the members are equal (theoretically) or at least a bunch of experts inside the membership.

One can also see the blog as a forum where the moderator would be a dictator who control the conversation, allowing only comments but not topic picking.

One can see a forum as a blog where the microphone would be opened for all, in as much as the conversation is not out of order...

The differences as a matter of fact lie on "the agenda setting" which is focused towards outside (for the blogs), and towards the interior (for the forums).

In other words, the blog has a vocation (even at an homeopatic dose) to "modify our perception of reality" ouside of its space by generating comments or post elsewhere in the blogosphere (or Internet in general). The forum limits the range of its agenda setting to its own internal space (i.e. that it is necessary "to come" inside the forum "to be heard")

From my point of view, I would tend to use the following tools in this way:

• blog is a space to develop an point of view
  


• forum is a space to develop a topic


• wiki is a space to develop a document
• 
  
• email is a space to develop a message

It is about of content creation, but each of them seems to be specialized to allow easily a specific kind of output. That said, you can do what ever you want, but bear in mind it might be less optimal...