What is the purpose for the wall???
If it's simple retention for a short period of time it might work.
A well built retaining wall with block will last as long as the concrete blocks. A earth bag wall will only last as long as the bags.
I was doing some reading on the bags, and they said to use good polypropylene bags. I don't know about you, but I've never seen plastic last any longer than a couple of years exposed to the elements, and burlap just breaks down.
Is your customer trying to be green?? If so, plastic bags aren't a good choice.