Microsoft investment in Silverlight ended with the release of SL5 in December 2011.
Earlier in 2011, some of the people behind Photosynth started a new project in Bing Maps, entitled Read/Write World.
http://bit.ly/readwriteworld (More videos)
Their goal was to complete some of the initial Photosynth vision from back in 2006 that the 2008 release never got to, such as linking photosynths, panoramas, web photos, videos, spin movies (inverse panoramas), and map data into one cohesive whole online.
They created a new markup language called RML (Reality Markup Lanugage) to refer to existing formats and add additional position and orientation metadata.
Another of their goals was to have an RML viewer written in web standards and open sourced so that anyone interested could port the viewer to the language/platform of their choice and contribute it back to the R/WW development community.