Sony officially won the video format war when Toshiba threw in the towel Feb. 19.
It's widely accepted that support from film studios put Sony's Blu-ray format over the top. This Wired article provides insight into why the studios chose Blu-ray over HD DVD.
Both Blu-ray and HD DVD formats use an anti-copying system called AACS, which has already been cracked. Sony's Blu-ray also includes BD+, a sophisticated DRM system that can be patched, as an added layer of protection. BD+ has yet to be cracked, and Lionsgate and Fox studios both cited DRM as the key reason for selecting Blu-ray.
BD+ was created by Cryptography Research, which offered the technology to both Sony and Toshiba, but only Sony elected to take it up on the offer.