Evaluating sources is how you:

• learn to answer the popular genealogy question "is this source correct?"
• learn to appropriately use ALL the sources available for your problem
• build a solution to a brick wall problem when no source exists that gives you a solution

Don't build your family tree on shaky ground but don't leave yourself stuck because you'll only use "good" sources (and you're out of those!). Source evaluation let's you use what you've got whether it's a great source or a poor source.

Every genealogist is limited by the sources that exist for their problem. Great genealogists know how to evaluate what they've found so they use it appropriately.