Okay, so I was just now playing around with Google Earth, when I looked up Seattle and found this...
Now, I know it's just a coincidence, but think about it for a minute. What if the "Foster's" in "Foster's Home for Imaginary Friends" isn't reffering to Madame Foster, but this so called Foster Island? It's the same as saying Seattle's Home fIF, or Brooklyn's Home, etc.
Now, I know some of you will reject this theory, but I just wanted to inform you guys of this.