Rename the Admin access path (wp-admin)

Will it couse any problems if simply rename it?

Many. Why do you want to do that?

My best guess is a security thing. And if that’s the case, you can always put your WP installation in a different folder of your site than where your blog is. ??

Theoretically, you could do a search and replace, but you are looking at well over 100 instances in the core files alone, and there is no way to know if it will work.

As an aside, wouldn’t it make more sense to use PHP constants for the default WP folder names?

Edit:
One reason would be transparency when using WP in a heavily customized CMS. Several times I’ve wanted to do something similar.