But was it the right decision?
Despite this, was Microsoft right to move on?
Open sourcers might chuckle at the predicament of the Windows fan: if Siverlight had been an open source project, they might argue, then Microsoft's army of programmers wouldn't been left hanging when the project's primary backer changed its roadmap.
The future is certainly uncertain for Silverlight's users, despite Muglia's enthusiasm and attempts at damage limitation. Customers, partners and individuals must now decide their next move.
There are some flagship early adopters — NBC streamed its summer and winter Olympics coverage while Netflix built a Silverlight media player. There was plenty of enthusiasm from a number of partners who felt — finally — that they had an alternative to Adobe Flash. In just three years, the Silverlight player had become installed on "two-thirds" of PCs.
Despite this, Silverlight remained heavily outgunned by Flash and HTML5 as a content authoring and delivery platform on the web and devices. Much work remained to push Silverlight's adoption by key partners and grassroots adoption among those in the wider content community.
A brilliant afterthought to the heavy WPF in 2007, Silverlight quickly became Microsoft's Flash. In 2010, it became a victim of history. With Apple banning Flash from the iPad and iPhone, and with Silverlight still not running on iOS, being "the other" Flash was a dangerous and limiting label.
It's notable that Muglia highlighted the fact that HTML5 can and does work on Apple's operating system. Clearly, Microsoft believes there's more to be had from having apps and content built using Microsoft tools and services than in continuing to push its own vision for a Flash-like player.
Backing HTML5 also suits Microsoft from a cost and maintenance perspective: in supporting HTML5, Microsoft can lower its overhead because it's not rolling its own stack of media technologies, while — handily — being perceived as being more open by backing HTML5.
The company is already showing in IE9 that it can work with existing standards and make them work better, without having to build its own version of a media stack optimized for Windows.
Muglia took a tough — and decent — decision to acknowledge that Microsoft's priorities have changed on Silverlight versus HTML5. This is clearly taking some getting used to among Silverlight users, and it'll be interesting to see if Microsoft feels stung and back-pedals.
If Microsoft doesn't go backwards, the next question will be just how far Microsoft continues to build Silverlight, and how far today's version of Silverlight separates and morphs to serve Windows Phones and PCs. ®