Do not panicccc!!!! you will see board members of companies everywhere selling stock before year end to avoid Obadummys' new tax rates relaxxxxx, your on the Krogerrrr train and the ride is smooth.....
Kroger has a strong stock option plan. The sales you are seeing are options expiring in 2012 or 2013. (Possibly later. The exercising of these options is happening because of the tax consequences in 2013.) Most execs that have these large blocks of options have to exercise and sell because of the $ amounts needed to exercise. Example: The COO has 64,000 shares expiring at $16 per share. To exercise and hold he would need to put up $1,024,000. If he exercises and sells at $27.50 he puts up zero dollars and walks away with $736,000 before taxes.
Even high paid execs don't , in general, have a million dollars plus laying around that they can put into company stock. Now he can take his profits and diversify his portfolio. I'm sure he has plenty of company stock in his retirement plan.
By the way Kroger, issues options to management at the store level and even some hourly employees.