When I was in college I remember reading an interesting study done somewhere about teenagers that had problems with math. They had found out that many of those students who were struggling with math had never crawled as a baby. They had skipped that step in development and had gone straight to walking. They taught these teenagers to crawl, did crawling exercises in class, and their math skills improved significantly. I don't remember the details of the study, but the idea obviously stuck with me and I became VERY excited as each of my children began to crawl. (Especially my little girl because of all her special therapy that began when she was only 6 weeks old. Another post for another day.)
Now, I'm not going to say that all non-crawlers will struggle with math. Neither will I say that all who struggle with math weren't crawlers as a baby (I crawled and am not good at math at all...I won't mention how many times I repeated math classes.) But I will say that crawling is a very important part of development. And Math isn't the only area it seems to affect. There are many studies that show how it affects the brain development (coordination, memory, etc.), and there are many theories out there including the possiblity that it's a factor in ADHD.
So, basically, don't push walking when your baby is enjoying crawling-this is an important time for your baby's brain to be getting a work-out, but if your baby skips crawling, maybe when he/she is an older child you can think of fun crawling games later in life to get them moving on their hands and knees.
* And here's a good article if you'd be interested in learning a little more: medcentral.org