I think the problem is that Ancestry (since that's who we're talking about) has two basic settings - all or nothing.
The consensus of this debate - whichever side of it you're on - seems to be that those who take their research seriously are perfectly willing to exchange information with those who are doing the same. The only disagreement is regarding the current 'wide open' mechanism which results in far more takers than givers - many without the courtesy of a request or acknowledgment and often mangling years of work to make a square peg fit into a round hole.
There will always be those who are happy to let anyone help themselves and do whatever they like with it, and others who will be offended by such an approach. I'm in the latter category.
What perhaps the 'everything should be open' camp don't 'get' because its not in their personal make-up is that often an emotional investment goes into these trees. They aren't just a giant jigsaw puzzle to some of us, and just as we guard & protect our living family we also guard & protect our deceased. Dave says he doubts his deceased grandparents would be too bothered about being branded a bigamist or having illegitimate children and he's right - but if that was my grandparents, both of whom I loved dearly, then I would be bothered about it. Very much so.
However, regardless of that aspect of things I must admit to being very nonplussed at the apparent belief that just because someone pays a sub to Ancestry its their God-given right to access personal family documents that may have a very deep meaning to me, along with information I only have because I also paid subs to various other sites to obtain it. I'm happy to share if you introduce yourself and ask, I just don't think you should expect to simply walk in and take it without any thought to how I might feel about it. To me that's just basic manners, and if you cant display those then why should I give you anything at all?
Unfortunately its this "I'm entitled to have whatever I want and I don't give a stuff about you" attitude that underpins why so many trees have gone private, mine included.
Anyway, I'm leaving this thread now as I too am uncomfortable with the tone of some of it.