Have you ever used boxes as a form?

I know a lot of you use styrofoam to make items lighter but what about cardboard boxes, beach balls, or other containers like liter soda bottles? I am considering making a very long, as well as tall wall, with faux cement stones and wanted to know if anyone ever used boxes to keep the weight down and to make it easier to move into place. What other items would you suggest and what items would you not use and why (so I can develop a thought process here). How about egg cartons-would they work?

Linda