In reply to Fredt: With so many questions there are conditions to the answer.
Recently I climbed with someone who never got his gear or rope out but only climbed on my gear (Not anymore, very quickly got wise) He was hopeless at placing gear, usually placing it when he realised he was about to fall, so it was slammed in and swung on. I am, fortunately quite good at extracting gear, but do not doubt for a minute that if the gear had been stuck he would not have offered to replace it.
If it is my fault gear is 'lost' I offer to replece it. If it is one of those 'climbing incidents', I offer to go halves. I expect climbing partners to do the same, and now outline my thoughts to all prospective partners. I would usually turn down offers to replace or go halves, as do my current climbing friends. If others don't like this arrangement they are welcome to go climb with someone else.