The theory is that purchasing stock on the open market and retiring it will increase the share price. Same value divided into fewer pieces should make the pieces bigger. However, according to Keynes, "The market can remain irrational longer than I can remain solvent." No guarantees, but if it does work, he's hoping that selling the stock at a profit is a more lightly taxed capital gain rather than the rate on dividends.
Actually, I'm not so sure. Since the dividends are "qualified", they're only taxed at 15%. Gains tax could be higher if you're in the upper brackets. N.B. I'm ignoring the AMT because no one, myself included, understands that.
Dino