Read Che's excellent posting The Tower Of Babel

In The Tower of Babel* Che postulates** talks about how social media (blogs, wiki's, online forums and the like) and, more specifically, the threads within them have a natural life cycle where the information*** grows and declines in 'usefulness'.

I suspect the effect he accurately describes happens not just online. For instance, many a time I have started a conversation with a bunch if people (be it at work or not) and, as the conversation, follows it own path the original usefulness to me wanes. Eventually, as it reaches it's natural conclusion, there's normally a silly joke, a controversial statement or a silence that indicates that it is no longer useful to anyone.

The starting point and the ending point are not connected in anyway but that's the beauty of listening and (hopefully) learning from others. Usefulness can come from the unexpected meanderings of people's brains and not just in a linear form.

Not all the time - sometimes we speak like "males", passing information only, and after three sentences it's all over.

* An excellent yet missed opportunity to have named it The Tower of Babble ... ;-)
** removed for reasons of pretension
*** I dispute Che's use of the word "knowledge" as I believe that only resides within humans or other entities of a high(er) forms. See my (slightly old) definition at my KM wiki: knowledge