One of the many reasons that advertisers never really signed on to advertising within digital, downloadable media is the measurement complexities. It's hard to know how people are using that media when they leave a website. Fortunately, after months of formal review, several members of the Association for Downloadable Media (ADM), including NPR and PRI, have agreed to support standards for advertising formats and audience measurement.
The supported ad formats include pre-roll, mid-roll and post-roll insertions, product placements and host endorsements. The list of download measurement guidelines is actually quite interesting, addressing native and third-party measurement issues, as well as the data contained in log files - from IP addresses and time stamps to topics like byte range and bytes served.