Who can start conversations?

In the past, companies had huge departments for marketing. Marketing means that you send your customers your message. You speak, and they listen.

But then came the Cluetrain, followed by the Hughtrain and we started conversations. The ideal tool for conversations is the weblog. On the corporate weblog you can write down your thoughts, and the readers can comment on that.

To me, this still does not feel alright. It is still the company who decides on the conversation topic. I can participate in a conversation, but I can't start one. OK, I could write my opinion on my own weblog, but wouldn't it be nice to have all conversations together?

Is there any tool that allows others to start conversations?