ldeva

Never worked with Joomla, just read about it. But I thought it already had these features built in, no need for a component...guess I was wrong.

I think Backtype has already one...but this is interesting to see how it evolves. I know uberVU and Disqus partnered and powers now the conversation tracking on Mashable. Let's see what Artiklz.com will respond (another competitor)...

I think if the inventor has sales skills that would be helpful.

You could try also Cubecart or Opencart...but it also depends on what do you want to achieve. Some carts are more complex than others...

Then what would be a good architecture for such a service?