It's interesting you say that. The very next article on the linked blog talks about Blockbuster Total Access (where you could rent online or in stores) taking a million customers a year from Netflix in 2007. Investor Carl Icahn ended up forcing out the CEO who championed Total Access and the new guy sold the membership list to Netflix for $1.4 billion. Streaming might have still catapulted Netflix past Blockbuster, but it would have been much tougher to sign all those content deals without the steady cash flow from DVD's.
Now it looks like Netflix was inevitable, but it took a few huge blunders by other companies for them to succeed. Remember when Starz basically gave away the rights to thousands of shows and movies (for $30 million/year)? We could just as likely be talking about Viacom Streaming and all those silly things that Netflix did.