I know they blow at people and maybe predators. Every time I hear a deer blow off in the distance i think its someone sneaking in and hunting. What else could they be blowing at?

they will blow at anything they feel like. seriously.

I've seen/heard deer blow at other deer. It does make ya wonder though.

I had a dominate buck one year come into the same thicket that does were visiting regularly and for 3 days straight he would enter the thicket and blow and blow!! I knew it wasn't at me because I could see into the thicket a bit and non of the deer ran off and the wind was in my face. So I wrote a deer expert about the experience and he told me a dominate buck will blow to let all the younger bucks to get the hell out and that daddy was home!

Had a doe blow (snort) at me once, when I came up on her fawn lying in the middle of the trail.

I had a big doe blow at a spike last night as he went into full sneak on her. Just letting him know that he is wasting his time. pretty funny exchange actually, I ended up literally laughing out loud in my stand. He was trying and she wasn't having it.

+1, i watched a doe blow and stomp her hoof at a house cat crossing a field 60 yds from her.