Since people wrote mostly positive things, here are some negative things (playing devil's advocate).
1. Globalization can ruin the environment. Moving things from one area to another wastes oil, etc.
2. Globalization can ruin local economies. There is a movement that wants to buy local - especially organic foods.
3. Globalization can lead to hyper-specialization, which can be good, but also negative. There is something great about being a generalist. Also what if something goes wrong. To know things generally give an incredible perspective that specialists do not have.
4. Globalization can be driven by people with "know how" and power and they can systematically fleece the world.