Just read a post by Kellie at She Finds Graves called "When Skeletons Should Stay Skeletons" that details some of her not-so-nice findings when researching the family tree. She quotes the old maxim about why genealogists research their families - so they know who to blame!
Isn't that true? Aren't we who go beyond just the names and dates and really dig into the whys and wherefores trying to figure out who we are and why we are the way we are? I'm not trying to re-open the debate about "family history" versus "genealogy" - if some want to think finding out the dirt is gossip, they are certainly entitled to their opinion. For many people, genealogy is seen as an expensive hobby, but it can be cheaper than therapy.
I'm not trying to suggest that the reason I act the way I do is 100% related to who my great-grandfather was - but I do believe that the choices made by my ancestors and relatives and how that family lore has been presented (or sanitized) has shaped how I believe my family was or should be. The journey of discovery has tarnished my view some ancestors and given me more respect for others, in much the same way that the closer you are to someone you begin to see them for who they really are, warts and all.
Finding out that the reason no one knows much about a relative is because they were conveniently "forgotten" a few generations ago can be a thrill laced with an "ick" factor. The question for me is always how to be tactful about revealing the truth. Even in my family's current generation (and the in-laws, etc.) there are "issues" that are not discussed openly - even if everyone knows about them. In a couple of generations, no one will be alive who even knows the facts and they will have to be "re-discovered" by a future family historian.