A long time ago, in a galaxy not too far away, this was once a feature. In fact, it queued up requests automatically. That said, it turns out it's illegal to have an automated request system that queues tracks automatically. As this would re-classify your radio station as an "interactive" platform and your royalty costs would be very very huge. So this feature was taken out.
Would you like to request a feature where it e-mails someone the requests instead? Please be aware though of the DMCA rules regarding requests. Refer to this FAQ at StreamLicensing.com's website:
http://www.streamlicensing.com/directory/index.cgi?action=page&page=faq
Dave Burton
I would like a request feature where listeners can browse selected playlists and make requests.