While it's true there are risks for using FOSS stuff Microsoft has left people high and dry too.
I used to think Microsoft was in it for the long game but it's pretty clear with what they did with WP7 and WPF/SL and now their replacement that locks you into W8 that it's "use at your own risk". There is no difference in Microsoft "supporting" a deprecated language, API, etc. or a FOSS project that goes dark. You can still use both stacks they're just not going anywhere. At least if you're desperate for a fix in a FOSS project you can get the source and fix it yourself.
That said I do give Microsoft credit for embracing FOSS stuff like node.js, jquery, etc. It helps balance things out a bit.