More the reason why these companies should of worked together on a unified format.
Sony defected from the DVD Forum because the forum (chaired by Toshiba) adopted Toshiba's blue laser technology instead of theirs.
Toshiba had promised the forum that HD DVD would be ready by 2004. Sony didn't think that was possible, and continued working on what became Blu-ray.
Turns out Sony was right, Toshiba didn't ship HD DVD until mid-2006.
In that same amount time, Sony had turned the Professional Disc for Data (23GB) into Blu-ray (25GB/50GB DL), created a Blu-ray consortium with many of the same members from the DVD Forum and signed on Disney.
The BDA ended up shipping Blu-ray around the the same time as Toshiba's first HD DVD player.
It's an interesting read.
By the way, both groups tried to merge in early 2005. However, Microsoft wanted the BDA to adopt their WindowsCE-based HDi technology. The BDA sided with Sun's Java, and merger talks ended.
http://www.roughlydrafted.com/2007/08/29/origins-of-the-blu-ray-vs-hd-dvd-war/