I was playing Corpse Party on my Vita once and thought it was part of the game because it looked like blood dripping down a wall.
Lol, I saw them a lot while playing Corpse Party too and felt they added a bit of creepyness.
I had a similar idea to this when I first saw my Vita's mura. If I thought about it being a unique identifier or "soul" of the Vita I felt a bit better about it.
My first Vita had a few horizontal lines along the bottom, a large dark spot in the center, and then some streaks and spots towards the edges. I eventually got tired of seeing that dark spot in the center and exchanged the Vita.
My new one looks like someone sneezed on the screen, but managed to miss the center. Just tiny spots around the outer edges (no lines) so I never see them during regular gameplay so I'm happy about the exchange.
I have a diagonal line or lightning effect down the right side of the screen. It is quite pronounced in darkness but the rest of the screen is pretty much clear except for a few small light blotches. I noticed it the first night when I was playing resident evil nemesis.