Man bør nok nærlæse dette inde man kaster sig ud i API'erne.
One should probably read this carefully before choosing an API.
Every time you add a widget or other external feature to your website you are handing over part of your web page experience and performance to a third party. The responsiveness and total page load of these external services is one way obsessive geeks tune and tweak their sites for optimal performance. Let's take a look at how the major mapping players performed.
Yahoo! offered the fastest performance, the smallest total download, and the smallest memory footprint in my tests. Microsoft's maps took a half-second longer to download and display than either of its competitors. Google had the highest total file count due to its mapping tile behavior.
Read much more: http://www.niallkennedy.com/blog/2007/08/map-api-comparison.html