Aside from lameness studies, weaves poles are just really neat to check out in slow motion.
Here is Kili who is quite proficient with the single foot technique and shows a very clean and consistent footwork pattern on both sides of the poles:
And here is Kenna at 14 months who has been doing a full set of 12 poles for only about 3 weeks now. She is very fast and looks great, however you can see that her footwork is not 100% consistent yet. In this video she tends to use one foot on the right side but two feet on the left. If I were to video her over several different sessions we would see that she sometimes uses the single foot technique the whole way through, and she sometimes throws a couple of double feet in. She's young and very green on the weave poles so this is just her figuring out the footwork that works best for her, and I imagine that as she gains more experience she will settle into being a single footer. On an experienced dog who typically uses the one foot technique, however, a video like this might indicate that the dog is experiencing pain or discomfort, most likely on the left front leg.