What I don't understand is, if Vita isn't region locked why not have one PSN account that can access content from all regions? I mean, if people want content that is in Japanese, but they're in the US let'em have it. Same with Japanese gamers who want games in English. Having 3 different stores with different content doesn't make sense. Have one account that can buy any of the content.
Because for some content the rights may lie with multiple parties depending on region. So if for example Sony would release Demon's Souls (I know it's not a Vita game, but bear with me) in the JP store, because they are the publishers of that title in Japan, and everybody could buy it, Atlus AND Namco Bandai would get screwed out of their money, since they have the rights for US and EU distribution respectively.
And that is illegal.