I ran across a stray dog. I decided not to talk to it because I know of some other dogs I would much rather have than this stray. So I just kept trotting on. It then attacked me, so I killed it.

1) Is it common for stray dogs to attack you if you don't talk to them?

2) Am I now in a position where I will be unable to recruit any other animal followers in the future?

Some stray dogs attacked me. Others just sit there looking at me until I talk to it. The stray dog will attack if its arched and keeps barking at you. And you can still recruit animal followers.

I had a stray dog attack me. No sooner had I killed it then its master, a bandit came running up. I think that explains it.

If it bothers you, learn the Calm spell or the Kyne's Peace shout. Then you can turn Mean Doggie into Nice Doggie instead of Dead Doggie.

I bet you had a sweetroll in your pocket

I had this happen once I was walking and seen him all of the sudden when I got close and stood there for a few seconds watching him he turned hostile and attacked me. I used calm to calm him down because my current character has a lot of love for dogs.

Thats what happened here. I stood looking at him for a few seconds, then ran on. All the sudden I am being attacked. I turn around and it is that dog.

I haven't unlocked Keynes Peace, other priorities at the moment, and I never bother with illusion spells, though maybe I should. But thanks for the tip. My first thought is usually my sword when I am being attacked. But I have used Kyne's Peace quite a bit for peaceful communing with nature. I am not too much into killing the wildlife, unlike many I have seen on youtube.

Lol yes there is a bunch of butchers out there.
But yes if you roleplay there can be other alternatives.
You can also run and go up and over a high rock and the dog cannot catch you if for roleplaying reason your character refuses to use illusion, that is if you do not want to kill the wildlife.

Your very welcome.