The latest release of desktop Twitter app TweetDeck launched with a ton of new features, which includes showing geolocated tweets. If a tweet includes the location meta-data, TweetDeck shows a tiny marker icon. Click the icon and you get a map of the location.
TweetDeck uses Yahoo's static maps, which displays a graphic, non-interactive version of the location. Static versions have come into favor recently, because there is only a single file to deliver, providing a faster experience for the user and decreasing the requirements of the provider. Static map APIs are also available from Google, MapQuest and OpenStreetMap.
Many TweetDeck users expressed displeasure with TweetDeck's choice of Yahoo as the provider, many suggesting Google be used instead. It's unclear why Google is preferred. It could be simply familiarity, or a perception of Google's map technology as superior. TweetDeck competitor Seesmic uses an interactive version of Google Maps in its web-based product.
However, the reason TweetDeck chose Yahoo is probably related to terms of service. Google expressly forbids using static maps in non-web interfaces. Unlike Seesmic Web, TweetDeck is installed on a user's computer using Adobe Air. Yahoo's terms do not appear to have the same prohibition.