Put a bunch on the ground and ask Isabelle about citizen satisfaction. She always tells me instantly that the people feel like they're living in a dump. It won't affect your perfect rating unless you leave them overnight.
My guess is that they will count as trash. I guess I could fish a bunch up and try to find out.
Hey, possible good news. I left ten eggs on the ground and Isabelle was cool with it. So, I jumped ahead to tomorrow, and she was STILL cool with it! I don't know if more will cause a problem.
I believe in new leaf that all items left on the ground count as trash but you are allowed to have a certain amount and still keep a perfect town rating. Having 10 on the ground shouldn't be a problem but just check with Isabelle every time you put down a new item.