I agree! Virgin mobile also does it.
Here's a quick summary of the three consumer MVNO's:
* Koodo offers $25 refer a a friend credits, you can refer yourself when adding lines, effective the moment you sign up with Koodo. Sometimes this credit doubles.
* Fido has the 10% off line 2 through 5, and has the $25 refer a friend credits, but you can only refer someone after maintaining service with Fido for a minimum of 15 days. They also have something going on with Spotify. But if you stream music via Spotify on your 3G/LTE data, you still incur data usage.
* Virgin Mobile also hase the 10% off line 2 through 5, but they got rid of their refer a friend promo years ago. They offer member benefits, but nothing for what most people need (such as groceries, gas, insurance).
Which MVNO is better for you depends on your lifestyle, cellular coverage, etc.