Yes, that's right neenztwinz, copyright is a totally separate issue, and will depend on the Terms and Conditions of the site.
The Intellectual property of the idea of the bulletin board is held by who ever invented bulletin boards (not necessarily in their electronic form): ditto for Blogs / Diaries.
But if there is a new idea posted on a bulletin board or in a blog hosted my MN - such as a fail safe method for making a baby go asleep, or a 100% guaranteed recipe for a self supporting birthday cake construction, say in the shape of Big Ben, then it will depend on MN's TnCs as to who has the IP and copyright on that idea.
If I have a fabby idea about a way of doing something / a new invention / a new song etc I would be fool to post about it in the public arena without first claiming the IP, and patenting it if it was commercial - .
To claim the copyright of an idea, and the IP you can lodge the idea into a copyright bank. Or have proof with a notary, or just have proof by posting it to yourself with a dated stamped letter (obviously don't open the letter!!).
As far as I know I didn't sign any T and C from MN when I registered. And I cannot find any T and C in the registration page now which allow MN to publish any of my posts without my prior consent. Anyone want to post a link? I've trawled through and still can't find it.
I think MN are in pretty murky waters with this one. Nowhere have I seen anything which overrides my automatic right to hold the copyright on the material I post.
Have a look at Copyright service
Their argument could be that the posts have no merit, and are not by experts - original methodology to getting a baby to sleep, or not - but we have to ask - if the posts have no merit, how come they are all going towards a book which obviously has merit?
So these posts to which we hold the copyright, obviously DO have merit, and MN is publishing them as their own, without our prior consent and agreement of terms.