The CalgaryLawyers.ca website states one reason why verbal agreements are a bad idea:
The biggest problem with verbal agreements (also know as oral agreements) is proving them. If one person says that an oral agreement was reached and the other party denies the agreement, it may be difficult to enforce the agreement.
From an auditor’s perspective, verbal agreements may be problematic because they do not generate a paper trail. I do not see problems with verbal agreements if they are later followed up by written agreements.
When I analyze a stock, oral agreements are a minor red flag. It may be a sign of sloppy work or stupidity. It could be more. One way to identify potential shorts is to look for these agreements (e.g. by using Edgar’s full text search). However, that is not how I find shorts.
Here are some publicly-traded companies with oral/verbal agreements/arrangements.