Always moving manufacturing to the location that has the lowest labor costs is bad for a bunch of reasons.
First, it isn't sustainable. There are a finite number of places with cheap labor. Once a place has been exploited for some period of time, the labor will eventually become expensive enough to force labor somewhere else. Eventually, you'll run out of places to shift the manufacturing to and you'll have to find some other way to cut costs.
Second, it sets up a boom and bust cycle. Manufacturing is great while it lasts. It provides comparably high wage jobs for comparably easy work requiring little education. However, it doesn't last. Since manufacturing will always move to where the labor is cheapest, the bubble will eventually burst and the factories will be closed and moved to the next cheap labor market.
Third, it has terrible consequences for the environment. Since the people making pennies a day to manufacture this stuff are too poor to buy it, it has to be shipped half way around the world to the markets where it will be sold. Not only do we have to ship stuff all over the world, but the pollution controls in the areas where the labor is cheap are usually much lower than the rest of the world. This is the hidden cost of this strategy that will be coming due very soon.
Fourth, it has terrible consequences for the people in the factories. Similar to the lax environmental regulations enjoyed by these manufacturing operations, there are also very lax workplace safety and worker protection laws.
For a long time, we have enjoyed cheap products at the expense of the environment and of the poor in developing countries. The seeds we have sewn are now starting to sprout. Our own economic well being is crumbling.