I’m surprised it was Narain that got the boot and not Liuzzi (not performance-wise, though) because Tata (Narian’s primary sponsor) is virtually the title sponsor for HRT. Likewise, Liuzzi is a much better benchmark for Ricciardo’s performance, so Red Bull must have payed a lot of money to overpower the Tata influence.
I am going to go out on a limb and say that Red Bull are so desperate to give Ricciardo a seat due to fear of him losing his coveted Formula Renault 3.5 Series campaign to Robert Wickens, Kevin Korjus, or even more embarassingly, Jean-Eric Vergne (a fellow Red Bull junior stablemate who has gotten far less testing oppurtuninties and exposure than his Australian competitor). This would be the third time Red Bull management pulled a driver mid-season from the World Series (following Vettel and Alguersuari).