said by donoreo:HTML 5 should be used.
HTML 5 video is missing three critical features to be a valid replacement for this:
1) Common set of codecs guaranteed by standard to be supported by all browsers. Firefox and Opera do not officially support h.264 or AAC, instead supporting WebM and Vorbis, despite 80% of HTML5 video being h.264.
2) DRM support. Doesn't matter how you feel about it (personally I hate DRM), content providers won't make their content available without it.
3) Seamless switching between multiple bitrate streams. You can do dynamic bitrate switching with javascript, but it's not seamless like it is in Flash/Silverlight (there will be a pause).
Not to mention that only three quarters of browser claim any HTML 5 support, and installing a browser plugin is a lot more realistic than asking somebody to change to a different browser to view your site/stream.
Until these issues are resolved, HTML 5 won't be a valid replacement for video streaming for Netflix or similar things. Point 1 should be resolved shortly, as Mozilla has said they will eventually switch to h.264 (due to WebM thankfully never catching on). Point 2 is something under discussion, but nobody has yet to agree on. Point 3 is something that isn't currently supported, but might be in the future.