@Peagles: I guess it reminds me a little of interlacing yes, but not quite like the kind of interlacing you see on modern TVs. I've never seen a PSP 3000 screen so dunno. Don't you have a GBC to try it with?!
And I don't have a DS Lite specifically, but I've never seen this effect on any other DS screen. Or any other screen at all for that matter.
Edit: To be clear, the GBC screen only shows this "interlacing" while you're moving it around in front of you. Not if the game itself moves/scrolls/whatever. At least from what I remember. I rarely play on my GBCs these days.
Yeh I have 4-5 sitting around here but never really noticed it before. I only mention the PSP3000 because it was a major sore point for people at the time it came out. My friend sold his to me and bought another 2000 because he couldn't bare it, it's not something that's very noticeable to me though.