DylanBC wrote an answer about Backcountry Access Tracker DTS Beacon on November 24, 2012
Bob, I have three reasons to add to Ben's:
1. Batteries work much better if they stay warm, and will stay warmer if they are deep in your layers. This doesn't make much difference when spring skiing at +5C in BC, but can make a difference when out at -20C in the Yukon - not huge probably, but possible significant
2. If it is always in the same place, you don't have to thrash around trying to figure out which layer it is in that day or at that moment
3. (Probably the most important of my reasons) During the course of a day, you might put on and take off layers ten or twenty times (sometimes I go from three layers with shell to shirt-sleeves and back and again inside an hour)... it would be bad if the beacon ended up either getting dropped or put into your back-pack.
I could be wrong, but I'm not sure about a jacket getting ripped off during a slide, at least if it is properly zipped up as it always should be on a descent, but being in a jacket certain increases the risk of it getting smashed.