The main problem with using the objective$-$and$-$task approach to setting an advertising budget is that

it takes the view that sales create advertising rather than advertising creates sales.

it often results in overspending or underspending of the firm's resources.

it does not achieve full potential in terms of stimulating demand.

the marketer may experience difficulty when trying to estimate accurately the level of effort needed to achieve goals.

it is difficult to determine the objectives of the campaign.