Gosh I am glad to hear I am not the only one with an easily distracted feeder!
My 7 month old DS started actually refusing the breast if we were out and about when he was about 5 months - he was too interested in what was going on around him. I can laugh about it now but man I ended up in some messes and milk everywhere! Totally different to my older daughter who once she was feeding the house could fall down and she wouldn't have noticed.
I have to go into a quiet room to breastfeed him, he seems to be ok with drinking from his cup though, still mucks around a bit though and take his time!
I tend to think that he can't be too hungry if he isn't fully focussed on it.
I put it down to just being normal baby behaviour