Companies using Drupal for business-critical functions?

Hi everyone,

My company is in the process of choosing a solution for replatforming our main site, which is going to be a pretty big project. We're using Drupal for a smaller, simpler publishing site, and Drupal is now on the table for the main site. Some of the other stakeholders have asked what I think is a perfectly valid question that I don't have a ready answer for, so I'm hoping some of you can help me with this one: Are there any medium- to large-sized businesses using Drupal for their main revenue-producing sites?

I've looked and haven't turned up any good examples. Most of the high-profile case studies use different solutions for their ecommerce functions, even if they only sell tchotchkes (ie. http://store.theonion.com/ - at least, I couldn't verify that this was Drupal). The big music sites (Pink, Britney Spears, etc.) list products, but then link to the label's main store. It seems like enterprise teams are happy to use Drupal for publishing content, but haven't made the leap to betting on Drupal to sustain a serious revenue stream.

Can anyone point to a good example of a recognizable brand using Drupal as the basis of a transactional, revenue-producing site?

Thanks in advance, I appreciate your interest and your help.

-- Dave