It would greatly promote the payment of dividends, and more ethical corporate behaviour. Currently, most public companies don't pay dividends - they'd rather retain the earnings (if earnings really exist) and this sometimes allows corporate executives put those earnings to dubious purposes...

as recently explained by that wonderfully reasonable, centrist publication BusinessWeek:

"A change in the way dividends are treated has much to commend it, not least the fact that these payouts are a check on corporate malfeasance. Indeed, before audited returns became the norm, dividends were management's way of proving that company profits were real rather than cooked. "Management can't pay cash to shareholders unless the cash actually is earned," notes Edward Yardeni, chief investment strategist at Prudential Securities. Adds York University's Milevsky: "I like the notion of not having double taxation. It appeals to my sense of fairness."

Rank-and-file economists have long advocated eliminating the double taxation of dividends, as have a number of Administrations, including those of Ford and Carter."