There is probably a good reason for it...
An online bulletin board isn't really taken serioulsy in most cases... and if something is said, it is usually an opinion, which is never defamation or in this case, libel.
If what is said can be found to be really an unbelieveable statement, or in legitimate jest, then it wouldn't really be bad... hence, they made this act up to protect those people and the courts (from getting overflowed with lawsuits) of this type.
Now, I'm sure, in certain situations, the Act would not apply.
C