I'm not sure how long it will last as a business, but CastingWords is remarkable for a simple reason - it's build upon both Amazon's Mechanical Turk and their new Simple Storage Service (S3). The podcasting transcription service sends your MP3 over to MTurk for the transcription, and the 'casts are seemingly hosted with S3. This slightly-outdated quote from founder Nathan McFarland (via Business 2.0) sums it up nicely:
The idea is to sell search ads against the keywords in the transcriptions, which we generate using Amazon’s Mechanical Turk and some whizzy software. But we need capital to pay all those MTurk workers, so in the next few weeks we’ll be opening a store. It will allow Podcasters to purchase transcriptions of their shows. We’ll do the transcriptions and give them a full transcription - not just chunks pulled back by the search engine if it happens to index their show. Of course they automatically get listed in the engine, so this arrangement should drive traffic to them, get them transcripts, and get us the cash needed to keep on transcribing.