OK, cool, but what does the penultimate sentence mean? "The scalability of App Engine is exciting but elusive; most apps won't need it and those that do won't u

OK, cool, but what does the penultimate sentence mean? "The scalability of App Engine is exciting but elusive; most apps won't need it and those that do won't use Google." It seems to me that apps which do need scalability will benefit most from the App Engine because they won't have to spend months hacking their own scalability infrastructure.