Answer - when it has so many tests and accountability hurdles that it becomes more of a burden to apply than to comply with the underlying obligations it purportedly seeks to exempt compliance with.
This is the risk presented by the "journalistic exemption" in the GDPR and found in the UK Data Protection Act. This is a key exemption but yet applying it to common media scenarios across news, print and TV production can be challenging and sometimes just impractical - the absurdity of journalistic exemption assessment forms in a fast paced newsroom for example. Even more frustrating for media organisations, is the fact that other territories subject to GDPR apply a much broader exemption or carve out journalism from GDPR entirely making the UK one of the most difficult jurisdictions to manage media data protection compliance issues in.
Interesting to see therefore that the ICO has announced that, following a pause in its work on the new journalism code, it has a new team working on it and finally plans to publish a draft for public consultation "over the summer". Definitely one to look out for and, in the meantime, they have provided an email address to feedback to. Practical examples very much needed!