I got this thought while watching the scene where Nagini attackes Mr. Weasley in the Department of Mysteries. We all know that Harry saw that through Nagini's eyes, as if he *were* Nagini. Harry is somehow connected to Voldemort, who has his own bond with Nagini, and so it's possible that's how Harry could do that, but wouldn't Voldemort have figured something was up if he were being used as a conduit between boy and snake?
I think it's because both Nagini and Harry are living Horcruxes, carrying pieces of Voldemort's soul. The other Horcruxes that we know about or can guess are inert - -Slyherin's Locket, Gaunt's Ring, Huffelpuff's Cup, Riddle's Diary.
And I think this will prove useful in the final book.