Hi Laura,
I see what you mean. I think that discussions on a message board are so different from face to face conversations, though. Having a conversation like this in installments over a long period of time opens the door to all sorts of interesting developments.
Here, we put out a thought by starting a thread and, as each new response is added, the direction of the talk can shift enormously, so by the time it gets to reply #6, folks are responding to an entirely different aspect than what was originally intended by the thread author. This dynamic is actually one of my favorite aspects of exchanges on the board, though ... I like to see the "spin offs" and various trains of thought that develop when people share. I hope that anyone who starts a thread and feels it gets diverted along the way will not take offense or walk away dissatisfied, but instead will return to try to draw focus back to the original thought when more discussion is needed.
In person, especially in the situation you mentioned with your pastor, whew... can you imagine his position? Everyone wants a piece of the pastor's time. Post service, he's got an entire congregation wanting to shake his hand or sometimes set him straight when they think he missed the mark, and all I can say is... I bet he'd like to get home and have his dinner!
I think that moms are in a similar difficult position. Our 10 year old son is one who always has a response for everything, whether it's a convo between my husband and me, my daughter and me... that boy has things to say!!

I think that it's good for kids to get the picture really young that sharing is one of the most important things to learn in order to live well and peaceably as a team. There's only so much time, energy, and other resources to go around and that will be enough if one is not always trying to grab it all. People get frustrated by different things to differing degrees. When a child has all her energy focused on gaining the whole pie for herself, I think she misses out on the opportunity to learn to appreciate how much fun it can really be to share. With my son, we don't tolerate his interruptions during the middle of our conversations and that takes constant diligence, because he simply overflows much of the time. When we're done, and if it's appropriate, we do invite him into our talk eventually, receive his input, and respond, so he doesn't get ignored. Through this process, he's learning to hold his tongue, to wait his turn to be heard, to not be a conversational bull in a china shop... and he's also learning that we value his thoughts and will listen when he doesn't barge in.
I don't think anyone intends to steal a topic here and leave out the original poster. Seems to me to be just a natural ebb and flow, with some topics "clicking" more than others and also, if a subject doesn't grab folks' attention right at the moment, it might at a later date. It doesn't seem so risky to put a topic out there when I look at it that way, because I know that everyone's not on the same page as me so I don't expect anything different. I guess it's all about expectations.
Love,
Hope