I think the term 'social bookmarking' has expanded from its initial, narrow definition of 'a service where you can bookmark stuff and share those bookmarks with others and potentially tag them' to the point where the general public will interpret it as to be wide enough to include sites like /., digg, reddit and HN, whereas before that time it was limited to sites like furl, diigoo and deliciou.us. Witness the title of this article. For me the key element is that the majority of the discussions use a link as the topic starter.

I understand that initially the definition was a more narrow one, but since this seems to be the way people use it nowadays I'll just go with the flow, I have no vested interest in seeing the definition being used in one way or another.

To me a 'forum' is a site where people will come to discuss a subject, occasionally using links to illustrate the point.

I think that it is not very friendly to try to label someone that is having a fairly long conversation with you a troll just because you apparently disagree with them.