As you know the biggest companies on the internet (Yahoo and Google) have created web applications/API’s and that have a positive effect on mapping applications and that’s the main reason that their number has increased substantially.
But not everybody has the same needs when it comes to accessibility. Most online mapping applications have the same purpose and the same options. That’s why for most of the users, these maps are kind of useless.
The design is totally separated from the data! You only have an image and a XML file!