Google used to display links to Google Maps, Yahoo Maps and Mapquest when you entered an address or a city name.
Now there's only a link to Google Maps next to a static map and a new option to get directions:
... and a simplified version if you don't type an address.
Google provides links to third parties in OneBox results if they don't have a service for that or if their service is not good enough. When their service becomes mature, there's no need for the other links. So I don't think it's fair to say this is an evil move from Google.
{ Via Blogoscoped. }