In an effort to upset more tree posters, here are a few of my pet peeves:
(1) Don't use an undocumented tree as a source, unless you note the tree is undocumented!
(2) Don't cite the wrong sources, if used. People have cited a marriage record for, say, James Elliot and Dora Lee, and the couple on the tree is James Elliot and Rosa Norris. The wrong record is as bad as no record!
(3) If your source negates info on your tree, don't use it! Pay attention people! Someone will post a well-documented will, bio, or other item that clearly shows that the person tied to that record is not mentioned in the record.
(4) Don't latch on to information, just because it fits. Research to find out if it does fit.
(5) Check your dates! Chances are Henry Willis [1789-1843] is not the husband of Alice Dunn [1770-1840]. The odds of Seth [b. 1810], Sarah [b. 1814] and Stephen [b. 1817] being Alice's children are slim as well. Some women did have children into their 40s, but not frequently - especially at 47.