"If Congress endorsed our proposal," they said, "these companies - and tens of thousands of others - would face a stark choice: They could endorse candidates or do business with the government, but they couldn't do both. When push came to shove, it's likely that very few would be willing to pay such a high price for their 'free speech'."
The court's decision also laid bare the silly arguments by conservatives that justices should merely interpret the law and not engage in judicial activism. The Scalia court first decided the outcome of a presidential election and is back to give a huge opening for corporate support of candidates (read: Republicans).
So I'll leave you with this thought from dissenting Justice John Paul Stevens:
"While American democracy is imperfect, few outside the majority of this court would have thought its flaws included the dearth of corporate money in politics."