Well your going to find conflicting arguements about steam on hardwood (especially here)

I personally tend to say its okay ONLY if the steam cleaner is properly working and doesnt leave excess water on the floor.

I also would only use the steam once in a blue moon. Never daily or weekly.

I tend to suggest to my customers that that dust mopping and spot cleaning with a chemical (hardwood approved) cleaner as needed.

And then when they want a disinfectant to clean i suggest warm water and a little vinegar.