The recent decision of Carl Hayman to play for the Euro's rather than the All Blacks (& a fair chunk of Taranaki) has generated plenty of debate about selecting NZ players who play for European clubs.
 
The recent experience of Butch James, selected to play for the Springboks this weekend vs Wales, should act as a warning to those in favour of it.
 

As the South African Rugby Union was also chasing the pound by playing Wales just a week after the Super 14 final they decided to select six players who play for European clubs (most of which are returning to South Africa next year to try & earn a place in their World Cup squad).  Of the six, Butch James played for an English club - Bath.  Having joined & trained with the squad the Butcher has now been forced to withdraw (not by his club but by Premier Rugby who run the English Premier club competition).
 
This only goes to show the self interest of not only the clubs but the administrators in the northern hemisphere.  As soon as the NZRU starts relying on them to release players for the All Blacks then we may as well look forward to only meaningless "friendly" internationals just like soccer.