User blog comment:FairyRaven/Exceeds and Earth Land Counterparts/@comment-904888-20120820112643/@comment-4829046-20120821041004

Uh...the Eggs were sent to places where there were strong magic users so as to protect them. Remember! Edolas holds Dragon Slayers in high regard so maybe they think that they are the mightiest mages in Earthland or something. These two are possibilities. In other words they WERE purposely sent near Dragon Slayers.

I just thought up another possibilty for Gajeel. What if the secret to unlocking true DS power is to eat a high degree magic element other than their original element. Natsu ate lightening before once. However Gajeel probably ate ONLY metal his entire life. His body was not used to handling that much foreign power so it might make him unable to be a true DS.