Social Networking Request=DENIED

So, I thought that this was funny. I was just searching through different social networking sites and I ran across some that did not accept my email. I am so used to being able to create a profile and sign up for anything that interest me on the internet, but this really came as a surprise. One that I was really interested in replied that my North Central email account was not one of their accepted email domains. So not only was my email not enough, but North Central had to be an affiliate of this site for me to even be able to join. WHAT?! :(
Here is one of the culprits: FledgeWing.com.