At this point you're probably thinking, "Oh yeah, I remember that game. But what does it have to do with genealogy?" I only mention it to make a point.
Most of us use information gleaned from published sources - from county histories to computerized databases - to connect the links in our family tree. They are a great resource, widely available, and often accurate. It is important to remember, however, that published sources are secondary sources of information, because they are one or more steps removed from the original records. Their quality and completely varies as widely as their content. Some online databases, for example, may have content that is three or more times removed from the original records (e.g. a computerized index, created from a published county history full of facts and stories collected by various authors from a variety of original and published sources), which greatly increases the likelihood of errors and omissions - much the same way that a sentence generally changes a little from person to person during the telephone game.
The Guinness Book of World Records, lists the first whisper in the current record-holding "telephone game" as "They inherited the earth and then the army came and scorched it." The final words passed on were "Mayfield College."
Published sources, compiled works and other derivative sources, especially the Internet variety, are full of helpful facts about our ancestors. When new information is found, we're justifiably excited, and tempted to immediately add the new details to our family tree (which is OK as long as you include the source of your information). Before moving on with your research, however - especially research based on these new facts - be sure to investigate the reliability of the original source. As time permits, you should also be sure to verify any facts found on your family through research in original records.