Since the shape of the blade is critical for air dispersal the freshener is better placed elsewhere.

It would unbalance the blade, causing it to wobble or shake. And if it came loose unexpectedly, it would be thrown across the room, possibly damaging something.

I think ceiling fan blades don't exactly have an airfoil shape, so sand, I think your objection ('critical') is a little nit-picky.

As for Dwane saying it will unbalance the blades, it will if it's only on one side, but the way I read this, completely_unproductive could also mean to put the scent oil 'on top' of the blades, meaning above them.

My big objection is that it really isn't 'easily' switched--I have to get a ladder to change the light bulbs already--this is higher than those. Otherwise, I imagine that spinning, with centrifugal force, they'd likely sling all of their scent oil out in the first hour.

I've never really understood the whole 'air freshener' thing anyway. You're not 'freshening'-you're just perfuming. Adding a different smell. If you keep your house clean, there will be a minimum of smells and you won't need to waste money on perfumers.

Imagine if you had an 'apple freshener' that would make rotten ones good again...yeah, I'd want one of those.

While I was a working industrial designer I had a project to design air freshener containers. The manufacturer admitted that it contained a chemical that anesthesizes the sensitivity of the nose rather than doing something to the air.

I don't know how you could interpret "...that attach to the top of ceiling fan blades" as "above the blades" rather than "attached to the blades".

yeah, I guess I read that wrong.