Scalability has nothing to do with your choice of framework or language. In terms of scalability, Cake, Django, and RoR are more or less equivalent (the first two are RoR clones after all).
I disagree that scalability has nothing to do with choice of framework. It happens that none of these frameworks address common scaling issues to a great extent, but that doesn't mean a framework could not do so.
Regarding the "RoR clones" claim, citation, please. Django was publicly released very shortly after RoR, having been developed privately for a couple years. I don't know about CakePHP.
