In RL talking about the same thing all the time will surely mark one as a boring conversationalist. Conversation involves give and take and a lack of attention to the other participant's interests will lead to talking to oneself sooner or later.
In a forum such as e2, "talking" in depth about multiple aspects of a single subject is called noding what you know and is a good thing. This is great when you have an deep interest in a subject.
I find breastfeeding to be fascinating, there is the physiology, the anatomy, the culture, the evolution, the economics, the mom, the baby, the dad, the family, the normal management and the management of unusual situations, etc..
My kids have said I can bring it into any conversation. This is true. I try to spare my family and friends (the RL thing again) from constant exposure to my obession(s). Here on e2 I can hone my writing skills while researching finer points and contribute something at the same time.
I'm also learning a new skill (HTML tagging), albeit in a very limited way, and having a ball meeting new people and reading about their obsession(s).
The specialist learns more and more about less and less until he knows everything about nothing at all.
A paraphrase of unattributed wisdom
This cool quote shamelessly yoinked from
Simulacron3's
homenode.