Cabin Crew are an important part of CRM - the wikipedia entry is wrong to suggest it is confined to the cockpit. If the relationship between cabin and flightdeck is poor then this has a clear impact on safety.
Undoubtedly, however it's the definition of relationship that's skewed.
It does not mean relationship in terms of how they interact social downroute. It's about clear concise communication of pertinent facts in a timely manner and focusing on the job in hand in an un-emotive manner.
Now undoubtedly for pilots there is a softer aspect to this as the actions of the pilot and co-pilot are strongly linked: they are carrying out different interlinked tasks at the same time.
However, for a large group of cabin crew carrying out tasks which are essentially stand alone how well you get on with the other crew really shouldn't be an issue.