You have probably heard this SharePoint slogan before: Do not use folders with SharePoint. If you are wondering why this is or need some arguments to convince a customer, then use the following list of reasons.

1. Structure
Changing a folder structure is complicated and time consuming, while changing a metadata structure is easier.

2. Authorization
Setting authorization on folders is possible but before you know it you have created an administrative nightmare

3. Findability
A nested folder structure is only know to the person who created it. Nesting folders will result in semi hidden files.

4. URL length
The URL Length is limited around 256 characters. All the nested folders names will be added to the URL which means you will run into the 256 limit very fast.

5. File Path
When moving files between folders will change the files path. This can result in broken links to the moved file.

6. Duplication
Multiple copies of one file tend to end up in multiple folders. This will result in version conflicts and possible misinformation.

7. Navigation: The user experience with navigating through folders is time consuming and confusing. It is hard to remember where you are and which folders you already checked.

8. Navigation
When a few sub folders down it is very hard to see where you are in the folder structure

9. Filter
You are able to filter within the opened folder, you are unable to filter all the document simultaneously. Filtering all documents simultaneously will speed up the searching process.

10. Sorting
You are able to sort within the opened folder, you are unable to sort all the document simultaneously. Sorting all documents simultaneously will speed up the searching process.

11. Losing files
When you place a file in a wrong folder in a lot of situation you know lost a file.

12. Forcing groups
Files can fall under multiple groups, with folders you need to store the file twice.