This risk is clearly noted in Justice Stevens' dissenting opinion:
"In the context of election to public office, the distinction between corporate and human speakers is significant. Although they make enormous contributions to our society, corporations are not actually members of it. They cannot vote or run for office. Because they may be managed and controlled by nonresidents, their interests may conflict in fundamental respects with the interests of eligible voters."Nonresidents are quite properly forbidden from spending money to influence US elections, but this decision opens the door to unlimited spending by foreign individuals, groups, and even governments. All they have to do is set up an American corporation or nonprofit, and use it to funnel as much money as they want into "independent expenditures". Perfectly legal. China doesn't have to bother with diplomacy anymore, now it can get what it wants by simply buying our elections.
It's the American way.