Have been bitten twice without provocation once when I was a child by a rough collie, & as an adult by a friends yellow lab. The second one was only a nip & my friend appologised & said she just occassionally acted that way & they hadn't worked out why.
The only other dog whose bitten me, not by accident was a staffie but he was fighting a friends Irish setter at the time & I was trying to help separate them, so it was my fault in a way.

I've never been bitten but I saw my Mum get bitten by my friend's Collie many years ago, when she came to collect me after tea (he had bitten several people). He knocked my Mum down and bit her full on the a**e and my Brother got bitten by my Aunt's friends JRT when we were visiting once. My Brother was dancing and the JRT just attached himself to my Bro's thigh