As with the extended payments processing dramas at National Australia Bank in November and December last year, the bank opened a hundred branches on Saturday to cater to the needs of customers aggravated by the failure of the bank's payments processing routines on Thursday.But they won't have been too busy, since the bank (unlike when the previous payments failure happened five months ago) managed to bring account balance records up to date over the course of 24 hours - something most customers will have worked out via electronic banking by Saturday morning.However, the list of branches deemed worth opening in the midst of a reputation crisis is more than a curiosity, since it is not even one-seventh of the bank's complement of 741 branches across Australia.Staff availability, and the bank's (and the Finance Sector Union's) security requirements, will have been one practical constraint on staffing. And some branches operate primarily to serve business or wealth customers, rather than the mass consumer market, which is (supposedly) now the target market for the bank. A look through the list of branches opened on Saturday raises interesting issues.In Tasmania, for instance, NAB opened three branches in the central business district of Hobart, one in the major shopping centre in the northern suburbs of Hobart and one in the centre of Launceston, making a grand total of five branches.NAB's presence in Australia's poorest state is pretty thin anyway, but branches in Sandy Bay - the wealthiest locale in the state - along three other centres in southern Tasmania were not on the priority list.Nor were the branches, which double as business banking centres, in Devonport and Burnie.NAB's customers in Adelaide and country South Australia would not have had much access to a branch at the weekend either, if they had needed to resort to the 2010 precedent of withdrawing funds over the counter at the weekend.And only six branches were open across the sprawl of western Sydney.While many of the more than 600 branches left shut on Saturday may pay their way, the lack of urgency attached to opening more of them casts an interesting light on an aspect of the bank's operating model that looks overdue for review.