Skateboard Bearings

Do the shields of skateboard bearings keep the lube in?

Everyone says that you only need the outer shield on your skateboard bearings, but wouldn't the lube or cream fly out into the inner wheel?
Ok, so one of my bearings can deffective. The shield was bent inward pretty horribly, so I took just that one out and threw it away I am going to be in trouble without a shield on one of my bearings?

To a point yes, there needs to be only a very little amount of lube in the bearings and what is needed is held in place between the balls and races. The shields only keep the lube inside if the bearings are spinning at a higher rate than would be obtained on a skateboard. The shields really keep dirt out of the bearings. It is by far worse to skate a dirty bearing than a dry one.

Skateboarding Tricks & Maintenance : How to Clean Skateboard Bearings Quick & Easy