I heard that was mostly FUD from microsoft, probably to use as an excuse to not support webGL. Read this: http://my.opera.com/haavard/blog/2011/06/22/microsoft
A few choice quotes:
"Microsoft's criticism would sound a little less hollow if they weren't doing the exact same thing with Silverlight that they are criticizing WebGL over. And lo and behold, a Denial of Service vulnerability in Silverlight 5 of the same type that Microsoft was overly concerned about with WebGL recently surfaced."
"Even people at Microsoft do not buy it."
I also recall hearing a bunch of the security issues have already been resolved.
Regardless, do those demos in Lucid's link actually use webGL or are they purely HTML5 canvas?