Final answer:
If reach and frequency are too high in an advertising campaign, the likely impacts include audience annoyance, limited reach, low brand awareness, and decreased cost-effectiveness.
Step-by-step explanation:
If effective reach and/or effective frequency are too high in an advertising campaign, there are several likely impacts. Firstly, the campaign may become too repetitive and annoying to the target audience, which can lead to a negative perception of the brand. Secondly, the campaign may not be able to reach a wide enough audience, limiting its effectiveness. Thirdly, if the campaign focuses solely on reach and frequency without considering the quality of the message and creative execution, it may not generate enough brand awareness. Lastly, increased reach and frequency may result in higher costs, making the campaign less cost-effective.