Providing Methodological Support to Colleagues Outside One's Expertise a Career Killer?
I can't think of a case where research or publications outside one's core area would have hurt an applicant, and would think that most departments actually think positively about it. What's important, though, is that the research and publication record within one's core area remains strong and prolific. If you only publish a paper every other year in your own area, but 2 every year with people outside your area, then a department might legitimately question how much you actually bring to their table.