Something I really have not thought about before (AS3 syntax):

private var m_obj:Object;
protected function get obj():Object
{
    return m_obj;
}

private var m_str:String;
protected function get str():String
{
    return m_str;
}

At least subclasses won't be able to set m_obj or m_str (though they could still modify m_obj). Is this just blatant overkill?

I am not talking about doing this as opposed to making them public. I am talking about doing this instead of just making the variables themselves protected. Like this:

protected var m_obj:Object; //more accessible than a private variable with a protected getter
protected var m_str:String; //more accessible than a private variable with a protected getter