By the way -- if all your players have the same background, try and find a way to tie it in to a plot/story.
How is it that they are all born under a bad sign... perhaps cosmic forces brought them together for a reason, etc.
As DracoSuave said, sure, it won't break the game since we're talking roughly equivalent to slightly more than a toughness feat. But at the same time, if someone chooses a skill-benefit background, they get less than skill focus would give them (also a feat) so getting a background benefit that is better than toughness (also a feat) is slightly (although not detremintally so) stronger than the other choices.
I personally just find it plain boring though.