This shouldn't make any difference, but a Marathon brings to mind a certain image that a Snickers does not. I am bound to pick up a Marathon when they return, but not a Snickers. That is slightly irrational, but a lot of the brand choices we make don't exactly rely on logic.
But the feeling that it is just a crafty sales ruse obviously niggles. Wouldn't want to fall for that one -;)
Wispa was slightly more interesting as the product had been discontinued. That was a hugely popular story on Brand Republic and generated a bit of debate.
What other chocolaty treats are there to be resurrected?