They can only pay dividends out of money they've raised or money they've earned. If it's the former case, they're just shuffling money from all investors to equity investors, and giving the government a 15% cut (so investors lose). In the latter case, the general taxable-income argument applies.
Actually, the general taxable income argument may still not apply depending on how previous loses are carried forward. Which really ties into another point I was going to make that companies are quite adept at minimizing tax exposure. The GAO reports the average corporation pays an effective tax rate of 25.2%. http://en.wikipedia.org/wiki/Corporate_tax_in_the_United_Sta...
