A (e.g., expected) performance of proposed ad placement is compared with a performance threshold (either an initial threshold or an adjusted threshold). The ad may be served if the expected performance meets the threshold (perhaps subject to additional conditions), but is not served if the expected performance is less than the performance threshold. Spend information of the ad so served is analyzed to determine if a target amount (budget) is expected to be overspent or underspent. If the former, the performance threshold is increased (and/or the ad performance value is decreased). If the later, the performance threshold is decreased (and/or the ad performance value is increased).