The European Data Protection Regulation requires the express consent of the user in order to continue browsing a website and this adds additional steps when users visit your website or click on a marketing piece. This means that there are more points in the user journey where visitors can drop or opt out, which can reduce the volume of data that is collected, such as browsing data on your website or the size of the audiences that are used in remarketing actions.
However, in practice correct application of the GDPR increases brand credibility and the trust of those users who accept the use of their data, so compliance with the regulation has positive effects in the long term.