I use Ancestry quite a bit... I started my tree about 3 years ago and have accumulated over 2000 people. However, what you said Andy is completely true. A few months ago, I started a new "official" tree in which everyone is 100% true and accurate. It's taking 100x longer, but I know it'll be worth it in the long run.
I even feel sorry for the people who have the invalid information without even knowing somethings wrong...
I have a girlfriend that has a tree with a couple thousand people. Mine is around 500 and that includes siblings of my
direct ancestors. I wont go past these shores, I don't have the experience and it gets to sketchy. What I have is solid.
One reason I started adding siblings is I have found info and photos in their trees that relates to mine. BUT as always,
verify!!!