I think the two are more inter-related than they seem at first glance.
At present, I don't own a Pony Bottle, and most of my dives have been in water and viz in which touching a buddy was required to see him/her.
Therefore, in my best efforts to BE a good buddy, I always make sure I'm within grabbing distance for an Octo or at least to be grabbed for the purpose of getting my attention.
I think, honestly, that if I had a pony bottle, I would be a lot less inclined to stay within 12-24" of my buddy at all times. If I can count on myself and myself alone during an emergency, the self-preservation instinct of staying close for a share-air scenario fades. Which does not result in a conscious effort to lose the buddy, but a less survival-instinct-fueled desire to always see a tank or fins, or something that belongs to your next breath of air.
Likewise - if both me and my buddy had pony bottles, the easier I think it would become to be seperated.
To date, on all my dives, I've been extremely and acutely aware of where my buddy was, for his safety and mine. I'm not saying a pony bottle will make me a bad buddy, it just increases the potential for that situation.
I should also add the following. And you can call me what you like or say what you want, but at the end - you all would do the same thing, so throw the rocks, but think long and hard before you pick up the first one.
My main dive buddy is my shift partner at work. I trust him with my life if I get into a situation where one of us has to use deadly force to effect an arrest or bust up a domestic dispute where someone is shooting at me. I know his wife, his family, we do everything together. I would be the one to tell his wife if he bought the proverbial farm underwater.
Every second he and I are underwater, we look out for each other. Either one of us would risk personal injury to help the other. It's happened at work several times.
ANYONE who says they will give that level of personal devotion to an instabuddy on a random boat somewhere is LYING to you.
Anyone who says otherwise is only fooling themselves.
You have to be self reliant if you are entering into a situation like diving. Which is why I have already ordered my Pony Bottle and setup.