The proposed reconciliation bill has a new 3.8% tax on investment income for taxpayers making more than $200K per year ($250K for married, joint filers). I don't know if the bill will make it through the Senate under reconciliation, but it's certainly got a decent chance. Note that investment income includes capital gains and dividends, so we're talking about the marginal tax rate on dividends going from 15% in 2010 to 39.6% in 2011 and up to 43.4% in 2013. The marginal tax rate on long-term capital gains will go from 15% in 2010 to 20% in 2011 and up to 23.8% in 2013.
That's a remarkable increase and surely will be priced into the stock market at some point.
When one considers that US corporations already pay a 35% income tax, then a corporation which distributes its profits to shareholders via dividends will essentially be returning only (1-35%)*(1-43.4%) = 36.8% of its before-tax profits to the owners of the company after they've paid their income tax.
For corporations which return cash via stock buybacks, (1-35%)*(1-23.8%) = 49.5% of before-tax profits are returned to the owners.
This surely must rank as one of the highest marginal tax rates on corporate income in the developed world. In fact, I'm pretty sure of it. Of OECD member countries only Denmark and France had higher effective corporate income taxes in 2009 (by 9.2% for Denmark and 6.3% for France), and the new rates in 2011 will put the United States in first place by a wide margin for profits distributed through dividends.