Not all the time, but sometimes, if I pick up my iPhone (3G) when it's just doing nothing... and look at the display, it has black streaks, kind of like the LCD is on, and displaying black streaks or lines, vertically down the display.

waking up the iPhone and then sleeping it again and it's fine, regular 'off' LCD... but randomly it displays these black lines/streaks.

take a look at your iPhone and tell me if yours does this too. It's very random.

I'm wondering if it would cause my battery to drain faster (because it looks like it's displaying black, on the LCD)... I wonder if I should get a replacement.

It works perfectly fine, but I've noticed this odd behavior...