Swaddling.........?????

Okay, before I had my som my MIL told me that she read an email that swaddling was bad recently. This was brought up because she asked something about the blankets in the crib(i can't remember exactly) and I told her we were going to use a swaddle me breathable baby blanket. I asked he why and se said she didn't remember and that I would have to look it up. I did and found nothing. I have never had anyone else tell me it is bad and even the nurses did it at the hospital. Is there anything bad about swaddling babies?