My employer received a court ordered wage garnishment for me today. The receptionist who opens the mail told me that it arrived, and asked me if I was expecting it. Our HR person disciplined the receptionist and told her that no one should have told me. Doesn't my employer have to tell me that money is going to be taken out of my paycheck?:(

No, they are not obligated to tell you. They can, though, tell who the creditor was.

But will they get in "trouble" for telling me? This is a close enough office that I would have thought they should tell me.

I don't see how they can get into trouble, surely there is a legal requirement to tell you... if only because you would suddenly have a surprise reduction of salary. In the UK, they couldn't even do this without a court order and you would be entitled to seek to defend it.

It will vary by state, in TN for example you are to be notified by the company doing the garnishment prior,
But it is not really wrong to tell you, but then they are not suppose to be discussing this outside of HR and management