Just to throw in my 2 cents, I don't ever add information willy nilly from someone's tree without trying to verify it first. However, it would be very nice if there were an easier way to read the information in trees than just family by family, and if I could print out the family line that would be even better.
Honestly, if people don't want their data copied, they shouldn't put it on a site where anyone can get to it. I don't care who has what of my information as long as they realize its all subject to error. And the only reason I put any trees online at all was to see if I could get contcts from people researching the same families. They're not updated and probably won't ever be since I work off FTM on my computer.