What are some other successful marketing campaigns by David the Agency?

The Google Home of the Whopper campaign by Burger King activated Google Assistant in people's homes through a TV commercial spot. The specific impact on Google Assistant's usage is not detailed in the provided content, but the campaign was successful enough to win a top creative award at Cannes Lions in 2017 and generate an estimated $135 million in earned media.

Some potential challenges of implementing a marketing campaign like Google Home of the Whopper could include backlash from consumers who feel their privacy has been invaded, technical difficulties in ensuring the voice command works properly, and potential legal issues related to the use of Google's technology without their consent. Additionally, such a campaign relies heavily on the novelty factor, which may not be sustainable in the long term.