I can wear a garbage bag liner in the rain and not have to spend $400-$600 on a fancy schmancy gortex coat.  I just bring a cheap roll of duct tape to repair it when it gets torn.  Then, I sleep in it so I don't have to spend $20 on a tent at WalMart, or carry all that extra weight either.  Best of all, I can usually get free garbage liners at any gas station or deli.  I just dump the contents of the bag right into the dumpster and, viola, I'm all set for my next outdoor adventure.  I like to get a couple extra, just in case.