Transloadit offers media upload, modification, and storage as a service for developers who need that functionality (or, as Transloadit's homepage puts it, "geeks who run web or mobile applications") but don't want to worry about it themselves. There aren't too many moving parts to it, but they're ones a lot of applications make use of. The Transloadit API's main functions include: file upload, image resizing, video file encoding, image thumbnail creations, and file storage on Amazon S3.
It might seem like a fairly niche market, but Transcode isn't the only company to target it. Drop.io, the file sharing service recently snapped up by Facebook, has been looking into providing a similar service with its Rich Media Backbone product. There's also the Zencoder API, part of an API-heavy Y Combinator class.
In many ways creating new web and mobile applications has been getting easier and easier. But some challenges—like media upload and processing—are likely to remain best dealt with at scale and outsourced by smaller companies and independent developers to providers that are more specialized.