In the *nix world, we assume '-' to imply stdout/stdin based upon the context. Wget correctly reads -O- to mean that the downloaded file should be outputted to stdout. However, Wget does not understand -o- to mean, "Log to stdout" instead of stderr.

E.g.:
`wget www.example.com`
will cause the logging to stderr and the file is downloaded as index.html

`wget -O- www.example.com`
will cause the logging to stderr and the downloaded file is printed to stdout

`wget -o- www.example.com`
will cause the logging to be saved to a file called "-" and the downloaded file is saved as index.html

However, in the last case, the logging should have gone to stdout. It should be saved to a file called "-" if the option was -o ./-