I created a list which uses 12 Person or Group fields. So I changed the resource throttling in Manage Web Applications > General Settings in Central Admin. Customer happy, so I'm happy too.
Now we have to the move this list to Office365 because their intranet is moving to the cloud. But changing the resource throttling settingis not possible in Office365 (yet?). So now we have to create a new solution.
So keep in mind when working with Office365, you can't change the list view lookup threshold.
*UPDATE*; waiting for reaction Microsoft if the settings will be made available in the future
*UPDATE 20110829*; Microsoft Customer Support has confirmed that the settings will not be available as of yet, but this may change in the future...