It seems some people have more badges than the length of the current badge list. Also, every once in while while looking at the badge list, the list appears slightly different as I notice a badge that I had not seen before. Is the list highly dynamic or does it change fairly regularly?
2 Answers
The badge list is not dynamic. But it is true that new badges are on a regular basis been added. Look at badge-request tag here on meta to learn about running badge requests.
Note that some badges can be awarded more than once, such as "Nice Answer". That's also explicitly mentioned in the badge description page.
Also note that tag badges (the ones with a gray background in the user badge listing) should not be confused with those badges. You get a bronze, silver and gold tag badge when you have earned 100, 400 and 1000 upvotes for answers in the tag in question.
See also:
It seems some people have more badges than the length of the current badge list.
In SO, people earn badges for votes received for a given tag (see "pivot" and "database" below). And other badges can be gained multiple times (see "Necromancer" and "Nice Question"). Those are a couple ways a user can earn more badges than the total count.