SPWebApplication.BlockedFileExtensions does not contain dots
Just a reminder post for me: SPWebApplication.BlockedFileExtensions outputs a Collection<string> that does not contain the leading dot.
However, Path.GetExtension does return the extension with a dot (or string.Empty in case the file does not have an extension).
Additionally, there may be upper/lowercase conflicts.
Using string to store Path is one of the biggest flaw in the .NET Fx.