Mobility is definitely a hot word in the fitness industry right now, and for good reason. It helps in all areas from recovery to performance. Having better mobility means you can more easily get into positions on Olympic lifts and traditional strength moves such as the back squat and front squat. Additionally, improved shoulder mobility will not only improve your kipping motion and therefore your pull ups and muscle ups, but also you won't be suffering from the shoulder injuries that plague some CrossFit competitors. However, this post is specifically concerned with ankle mobility and the quick fix often associated with a lack of ankle mobility - lifting shoes.
Walk into nearly any established CrossFit box and you're bound to see multiple people in Olympic weightlifting shoes. Some people even like to wear them during MetCons, although they are actually designed to be strictly worn for strength movements such as the snatch, clean and jerk, and back squat. The reason you'll see so many people in them, however, is because these shoes are a quick fix for ankle mobility issues.
When someone first walks into a CrossFit box, the chances are they cannot perform even a basic air squat with correct form. Since so many of us spend so much time sitting behind a desk, the reason for the inability to squat is due to locked hips and immobile ankles. Simply working out, along with stretching post-WOD generally opens the hips up well enough to squat correctly, but the ankles are a different story. They are more difficult to work on, and often times people look for a quick fix. The raised heel of the Olympic lifting shoe (check out the best ones here) allows your ankle to have to flex less when completing a lift. Basically, you get a slight "cheat" in the move.
Now, you may be thinking that the heel of that shoe looks about as raised as a running shoe, so what gives? Why do people use them? Running shoes are a terrible choice for weight bearing movements because they are extremely cushioned, meaning they actually absorb your power. Not what you want when lifting weights. However, flat shoes such as CrossFit Nanos (here) or NoBull Trainers (here) are firm and therefor provide power transfer, but don't give your ankles that same advantage. This is a good thing! You should be able to get into all the required lifting positions without the help of a shoe. If you cannot yet do that, don't put on lifters. Just as you shouldn't wear a weightlifting belt until you know how to brace your core, don't use an Oly lifter as a crutch when you cannot squat correctly.