[MoonZar]

Rich Baker comments on optional paladin mounts and paladin multiclassing restrictions:

We're leaning toward making paladin mounts optional, not a built-in part of the class. So you might gain access to a cool mount by deciding to take the right paragon path or spending the appropriate feat. Paladin players who don't want the complexity of a mount can avoid it easily enough, but those who do want the mount can still make the decisions to get a unique mount.

Paladin multiclassing restrictions are gone.