I think what Ibrahim recalls hearing about is the binding of biotin by avidin, a protein found in egg whites (albumen). Avidin is inactivated by heating. This source
is often referenced. There's considerable debate about whether this is a real concern (ie. how many raw eggs are you feeding?).
The other issue that is often discussed with feeding raw eggs with the shell is whether the eggs have been sprayed with a preservative or not (ie. ask your egg supplier). There's also debate about whether cooking the eggs makes the proteins more biologically available (ie. this is a debate in the MMA community too).
Like pretty much everything associated with raw feeding, look at both sides of the arguments and do what you feel comfortable with.
I feed boiled eggs from my in-laws' farm but that's more because I have to boil an egg for my husband anyway than being unduly concerned with the binding of biotin.