In an ideal world, every vessel would sail back with the same amount of containers it came with, just filling up with empties on the weaker leg of the trade. However, there are many, many factors that can hamper operations (e.g. port congestion, vessel being behind schedule, lack of trucks for empty repositioning, etc), which don't always let you use your space to 100% capacity.<p>A single operational problem can cause hundreds of containers to be stranded on the wrong side of the trade and sit unused for months. It's incredibly difficult to catch up and recover when you're at a space premium.<p>There's also the issue of inland transport. You could save 75% of empty freight costs with this.<p>However, I'm pretty skeptical of the idea in general, as containers are handled quite roughly and damage to the side panels is very common. If they cost x3 to produce, they'll probably cost x10 in M&#38;R.