I bruise so easily, and I really enjoy deep thuddy impact play, so fortunately, I actually like bruises. CONSENSUAL bruises I think they're kind of pretty (I know, what a weirdo) and whenever I look at them, they always remind me of the feelings and emotions I was having at the time I received them. And since I am terribly picky about who I bottom to (the list is short, and those on it are people I care deeply for and love), those are *always* good feelings
It is worth noting that most any mark (red hand prints from a good bum spank, for example) are just low level bruises. I understand the line that @sammi and @liz2 are drawing, however, as bruising does imply the purple/yellow/green variety of mark.
Anyways tho, to each their own! I never ever assume that play partners want bruises, no matter how deep a beating they want - marking of any sort is *always* one of many points on the negotiation table.