Why is this being upvoted? I will say it is a well written tutorial but the content is basically completely stripped from html5rocks. There is an overabundance of sites with this topic and a simple google will reveal that. I happen to know this because I was starting to use web workers about 6 hours ago. And yes, html5rocks does include the blob trick.
Where is your contribution? Usually if someone have better resources than the one submitted they post an array of links to these curated info.