There's been a lively conversation (such as it can be in 140 chars) lately about whether it is better to put CSS files on the disk in the _layouts folder or to store them in a Document Library in the Site Collection. This seemed like a good place to post the topic to allow some longer discussion about it.
As for me, I always prefer to avoid putting anything on the disk if I can avoid it. I prefer a Document Library for the CSS. There are many reasons for this, but here are some: versioning, fine-grained permissions, approval processes, they are a part of a Site Collection backup, touching the server can lead to problems, etc. I also don't believe that files on the disk will be served up any faster than files in SQL if SQL is managed correctly.
What's your opinion? Weigh in!