What is the reason why they allow only Americans to sign up? I don't think it's because of BETA. Americans can test the product so can non-Americans. In fact, if they ever wanted to go global, they would have allow everyone to test it equally. Remember, long time ago before YPN used the geo-targeting filter, if you happened to show YPN ads on non-us traffic, you could get banned. The word is "SEGREGATION". They asked you to segregate non-us visitors from viewing the ads. Don't ask me who got banned because of this. Search for the older threads. You'll find more than plenty.
Well, that wouldn't be about racism. That would be about location. America has all races. If you are in America Yahoo allows you in the program, regardless of your race. If you are outside America, or your website visitors come from outside America, you don't get to participate in the program. I had 7% non-U.S. traffic and got banned. Are they fools at Yahoo? Obviously yes. Are they racist? No indication at all of that.