Like most APIs, Google requires a key. The key is specific to a web site, which Google seems to define as a directory. For example, if you sign up with the domain mygooglemapssite.biz, you cannot use Google Maps under mygooglemapssite.biz/maps/. The good news is that one Google account (required to get a key) can have multiple keys.
Google Maps services need to be freely available. Also, at this time, Google is limiting sites to those with less than 50,000 page views per day.
And wouldn’t it be neat if Google automatically considered the ads it will one day put on API-generated maps to be AdSense ads?
The best one on the list: apparently Google’s API requires input by latitude and longitude. This might just be an intentional hurdle to stop everyone and their web developer mother from adding a map to their site. If you’re a Perl hacker, you could use this free geocoder program (also has a low-cost web service). I used this for my closest WiFi hotspot feature and I’ll also use it for the naturally forthcoming WiFi map.
Yahoo! lets you use all the input (address, intersection, airport, etc.) you normally can use. And Yahoo has given no limit (“within reason”) on the number of pageviews. Yet, I’ll be using Google’s. Yahoo! still can’t quite put it together like Google. Their clean, smooth interface seems to be loved by all.
Update: Google also distinguishes between www.domain.ext and domain.ext. My fix has been to look at the URL and then forward to the same URL with “www.” removed, but that’s pretty ugly.