In Europe (where I'm at), many universities have faculty, staff, students, and postdocs who are only part time. When I say part time, I don't mean split between two groups but rather 1/2 university and 1/2 other. In those instances, it's a terrible idea. For PhDs and postdocs, they seem more interested in working on their job outside of the university (where they get paid more) and for faculty, its impossible to run a group effectively when you're only there 2-3 days/week. (I know, because that's what I've lived with for 4 years...)
Supposedly this model is in place because the contacts with industry should bring in more grants and research money (and in some cases it does), but for those of us who are here 5 (6... 7...) days a week, we really see the inefficiency. At the postdoc level, it isn't as bad because they don't have too much management to do. However, when your advisor is never around, you really start to dislike your group.