Probably the most important technical development in securing multi-screen delivery is watermarking technology, primarily because the implications of adopting that technology will have the most profound changes across the entire content business value chain, including studios, theaters, retailers, and video service providers. Essentially, the dearth of available premium content is among the main obstacles to multi-screen video adoption becoming mainstream. In order to increase the availability of premium content, producers and owners of content want assurances that their premium assets will remain protected, while all members across the value chain want to assurances that they will be paid.
To be sure, there will be a sequencing of events for watermarking technology to help grow available content for multi-screen delivery. A May 2010 decision from the Federal Communications Commission (FCC) permitted unprotected outputs on set-top-boxes (STBs) to be disabled for video on demand (VoD). This regulatory decision to enable "selectable output control" provides a base level of protection against unauthorized copying of premium media assets. 
Watermarking is a central technology underpinning this shift in content availability. With watermarking technology, if the STB output control is compromised (a not unlikely occurrence), and an illegal copy of the movie is distributed, the watermarks inserted into the video stream could be used to identify the perpetrating source. In other words, unique watermarks are delivered into each video stream which can enable tracing illegal copies to their original legal source. While this does not protect assets, it acts as a deterred to piracy. Armed with legal authority, the ability to identify criminals could raise the stakes high enough to make content theft a less profitable enterprise. It essentially raises the risk and potentially the cost of being caught--both of which are insufficient to deter content theft today.
To date, watermarks for Pay-TV services have been inserted into baseband video at the client device, such as STBs, after the video is decoded and prior to its output for display (i.e. the analogue hole). Its implementation requires integration with STB chipsets. 
Despite the low processing requirements for watermarking, since the watermarks are inserted into baseband video, the technology's ability to scale has been limited. A different watermarking approach is required to address the scale requirements of multi-screen content delivery, where unique content streams are unicast over various networks and to multiple devices. Newer developments in watermarking technology leverage processing resources in the headend to efficiently scale the insertion of watermarks into compressed video streams prior to distribution. Content is pre-processed at the point of ingest to enable the identification, creation, and insertion of a compressed watermark into the compressed video stream that will be included in all downstream copies. No modification or processing is required at the client device. This makes headend-based watermarking a viable solution for high throughput environments, such as video-optimized content delivery networks (CDNs).
A major obstacle to broad adoption of watermarking technology is that elements of the content value chain are focused on protecting existing business models. Content owners are increasingly ready to adopt watermarking technology to expand their content distribution opportunities. However, their existing partners, such as video retailers and theaters owners see the outcome as a zero-sum game: earlier release windows and multi-screen delivery will lead to fewer box-office and retail sales. While watermarking technology is primarily being driven into the marketplace by two small and independent vendors (Civolution based in Amsterdam, and Verimatrix based in San Diego), it is unlikely that they will be able to independently drive adoption. Market success will require an evolution to existing business models--an undertaking requiring cooperation across the entire content ecosystem.
Yoav Schreiber is Senior Analyst for Digital Media Infrastructure at Current Analysis, and a FierceCable contributor. Follow him on Twitter @yschreiber.