Oliver Löffel published an interesting article for Lexology which concerns a case for a Black Friday trademark registered in Germany by a Hong Kong company that licensed this mark to a Vienne based company.
In a nutshell, the later company started to threaten every other company that tries to use this expression in advertisement campaign related to the well-known US day for bargain-sales.
It is no surprise that in this case many cancellation actions were been initiated against the mark on absolute grounds – lack of distinctiveness and a term which have become customary in the current language or in the bona fide and established practices of the trade. The reason for this is the fact that this mark was registered in 2013 whereas the use of the expression in Germany started back to 2006 when Apple use Balck Friday for its promotional campaign.
More information here.