LOL @ dixie and yankee robins! Nic it seems like they would be extremely vulnerable to predators with a nest on the ground. Most birds that nest on the ground have babies that are much more developed when they're born (like chickens and ducks, for example) so they are able to follow the mother and get out of harms way. Baby robins are almost embryonic when born - no way they could do anything but be eaten.
Well she didn't lay an egg today so I think 4 may be it. I'll post back once they hatch. We are thinking about putting a webcam up and streaming the vid. We'll see.