I like share repurchases, but unlike Buffett who picks his spots to deploy his cash, Exxon Mobil is much more methodical in its approach. When the company has excess cash, it buys back stock. That seems to be Exxon's default use for excess cash. There doesn't seem to be any consideration given to the actual price being paid for that stock.
When the stock price of Exxon went down in 2009 and 2010, the company actually bought considerably less of it. Why? Because the company didn't let the cash build up during high commodity prices of 2006, 2007 and 2008 and instead spent almost $100 billion buying Exxon shares. Does it make sense to maximize share repurchases when the stock price is high? Of course not, but that is what Exxon has been doing.