Filing for a Community Trademark has always included a gamble.  The costs for obtaining a CTM are lower than filing in the separate national jursidictions.  However a CTM is all or nothing – you cannot be successfully opposed in any CTM jurisdiction – there is no such thing as a partial CTM.  If you are successfully opposed in one or more jurisdictions, your CTM is ‘broken’ and you must re-file your surviving ‘shards’ in those countries’ national trademark office.  This is an expensive debacle.  This is also potentially an argument for using the Madrid system instead.

The most recently reported instant of a broken CTM is that of RUFFLES for Pepsico, which will lost the chance for a CTM based on a German company’s rights in RIFFELs for potato chips.  This article suggests that this opposition is based on Pepsico’s 1996 application (CTMs went live in 1996).

Community Trademark FAQs here.