The erythromycin is to prevent eye infection due undiagnosed gonorrhea, I believe. I was tested for STDs during my pregnancy, so we declined the eye goop. The vitamin K is to help with blood clotting, and since my son wasn't going to be circumcised, and did not have a traumatic birth (vacuum, forceps, etc), we declined that as well. I just find it hard to believe that ALL babies would be born without something that they actually need. Nature isn't stupid, ya know? Here is some info you may find interesting:
"As reported in the PDR and as published in the IM vitamin K packet inserts for Merck, Roche and Abbott, "Studies of carcinogenicity, mutagenesis or impairment of fertility have not been conducted with Vitamin K1 Injection (Phytonadione Injection, USP)."
"The manufacturers warn on the product insert: "Severe reactions, including fatalities, have occurred during and immediately after intravenous injection of phytonadione even when precautions have been taken to dilute the vitamin and avoid rapid infusion..."
http://www.vaccination.inoz.com/VitaminK.html