Not too scientific and somewhat speculation but I just noticed this and thought it might be helpful to others.
When you start the car, look to see how long your oil light stays on. If it stays on past the other lights, it could be an indication that some of your bolts around the oil pickup is coming loose or have fallen off. My light kept staying on longer and longer(we're talking fractions of a second) lately. Now it is a good second or two before it goes off after the other lights. It was never like that before.
I just noticed this along with the rattle sound coming from my oil pan recently and I'm fairly sure some of my bolts in the oil pan have fallen out. I will know for sure this weekend.
This doesn't necessarily mean anything but just something to observe in your own cars.