Andy_Langton - 5:04 pm on Sep 27, 2012 (gmt 0)

It's obviously a part of the algorithm if they are using it in this instance

That's a step too far, I think. You may also be rewarded with 'block results from www.example.com' when clicking back. So, I would regard this as an interface thing, not an algo thing. What it does confirm is that Google do not view clicking back as necessarily reflecting negatively on the site you just viewed.