Google has introduced a very important feature to Google Maps: MyMaps. Tucked into the sidebar on the left in Google Maps main screen, MyMaps enable everyone to create their own maps. The features are as follows:

* Mark your favorite places on your map.
* Draw lines and shapes to highlight paths and areas.
* Add your own text, photos, and videos.
* Publish your map to the web.
* Share your map with friends and family.

Obviously, this is going to hurt startups that based their business on enabling users to create Google Maps mashups, like Frappr, Platial , Flagr, and many others. Mashable is even going so far as to say that this means instant death for all Google Maps mashups, while Om Malik says that consequences for these startups will be dire. I’m sure that a small number of such services will find ways to stay competitive, but it’s obvious that a huge majority of them can simply close their business right now because it’s game over for them.

While this is definitely a legitimate move by Google, it raises questions on whether it’s smart to ever start a company dependent on another company’s data at all. I’d say that, at the very least, you have to be very, very careful and know exactly what your exit options are before starting such an endeavor.