[ScottBurson]

I had a manager who made a practice of thanking people when they did things he had asked them to. I hadn't seen it done that assiduously before, and I rather got to like it. I try to do the same now, when appropriate.

I agree, though, that pre-thanking someone before they've done what you ask is presumptuous.

[mgkimsal]

That pre-thank may be meant as "thank you for your attention to this matter" vs "thank you for doing the work".