The US PlayStation Blog posted "Five Things We Learned At The Japan PS Vita Launch", and in it they find Takashi Sogabe who's been working at Sony for nearly 30 years, and in fact designed the original Walkman. He also lets it go that the team at Sony had Vita in slider, and clamshell form factors before settling on what they call "the super oval". The blog promises a full interview with Mr. Sogabe in the next year.
The slider design isn't surprising given this was one of the early devkits:
UPDATE:
Full interview posted.
The slider design isn't surprising given this was one of the early devkits:
UPDATE:
Full interview posted.