I recently came across a large amount of free empty chicken feed sacks on Craigslist. I jumped at the opportunity and brought them home without much thought. Now looking at the sacks I noticed they have a thin plastic lining on the outside of the woven polypropylene that has all the product's info printed on it. I'm worried that if I use these sacks to build my earthbag home they won't allow the damp earth inside to cure properly. Has anyone tried these types of bags? Does anyone have any thoughts on this? Maybe the punctures made by the barbed wire between courses would be enough to allow for them to release moisture and cure?

If they are the same type feed sacks my chicken feed comes in they should be OK for what you are wanting to do.  Mine do seem more water tight than the previous type my feed company was using (they recently changed bag types as well).  You could test them by pouring water in one of them and see how it filters out just to be sure.  Might take longer for your dirt to cure and dry out, but it still should dry.