The developer community immediately seized on Google Maps and reverse engineered the API with astonishing speed. The service was, almost over night, integrated into a huge range of web and mobile phone aplications.
Today however Google released an official API for the Maps web service, and people have pointed out never has the community been so far ahead of Google and made me think. Did Google release the API because they always meant to anyway, or did they release the API because otherwise they were going to be left behind in exploiting their own service?
Update: Interestingly Yahoo! also released the API for their maps service today. Although as Nat Torkington has pointed out, they're approaching things from entirely a different direction.