If you’ve ever set up a WordPress multisite network using Askimet for anti-spam, you’ve probably been annoyed that there is no network wide setting. Turns out there is, in wp-config.php. All you have to do is add this in wp-config and you’re good to go:

define('WPCOM_API_KEY','your-key');

It would have been nice to see a settings menu in the network dashboard, but oh well, this works.