You’ve designed a shiny new website; carefully selecting the colors, typography and photographs to perfectly reflect the company's branding. Then your client asks you to add a map. Sure, you could use a map building ‘wizard’, such as the one that comes with every google account. But, let’s face it, their functionality is limited and they look pretty generic!
The Google maps API, on the other hand, gives you the freedom to create completely customized maps, which can do all sorts of cool things. ThePortsmouth History map is a site I built recently using this API.