18. The computer storage medium of claim 17 , wherein the first evaluation process and the second evaluation process are performed by the distributed computing system in less time than that required for the distributed computing system to perform a combinatorial evaluation process using the set of third-party content.
17. A non-transitory computer storage medium encoded with a computer program, the program comprising instructions that when executed by a distributed computing system cause the distributed computing system to perform operations comprising: identifying a particular presentation opportunity for a particular presentation of third-party content in various locations of a given electronic document presented at a user device; evaluating, based on information related to the identified particular presentation opportunity, a corpus of electronically stored third-party content to identify a set of third-party content eligible to be presented in the given electronic document; performing, by a distributed computing system and for the particular presentation opportunity, a first evaluation process using the set of third-party content to obtain a separate cost-prominence relationship for each third-party content in the set, including: identifying, for each location among the various locations of the given electronic document, an aggregate performance of multiple different third-party content when presented in that location of the given electronic document; for each third-party content: determining a bid amount required for that third-party content to be presented in each of the various locations of the given electronic document; and fitting a cost-prominence curve to points each representing an intersection of the aggregate performance at one of the various locations of the given document and the bid amount required for that third-party content to be presented in that location of the given document; performing, for a first location of the given electronic document, by the distributed computing system and independent of the cost-prominence relationship, a second evaluation process to identify a winning third-party content for the first location; selecting, by the distributed computing system, a format of the winning third-party content based, at least in part, on the cost-prominence relationship of the first evaluation process; and transmitting, to the user device, machine readable instructions that automatically configure the user device to present the winning third-party content with the given electronic document and according to the format, wherein the first evaluation process and the second evaluation process are both performed after identifying the particular presentation opportunity, before transmitting the instructions that configure the user device to present the winning third-party content with the given electronic document, and within a latency constraint for providing third-party content responsive to the identified particular presentation opportunity.