The picture is kind of a joke. If you take an inductor and put it in parallel with a battery, you have immediately high resistance, and very soon after, practically zero resistance. In essence, you short-circuit the supply. The resistor is there to show a tangible load -- since, without it, you've only created a battery destroyer. Or a space heater.
OK, so you're thinking putting a 12v regulator after the inductor would "regulate away" the positive spike. Well, two problems with that. First, the spike could very well be excessively high-voltage, subjecting the semiconductors inside the regulator to a good old fashioned pummeling. It's not the method of choice, at least. Second, depending on the transient response of the regulator, it could slip right through the feedback loop and on to the load. Typically, fast diodes with high voltage tolerance (100-1000v) are used instead where transient suppression is necessary. In reality, whether the load "sees" that positive spike or not is questionable. But if the application deems that it does, chances are a linear regulator will be just as susceptible to damage. Sorry, nothing's that easy.
I see. So you're making the battery the path of least resistance so that it doesn't suck the current and voltage from the camera. Won't the camera still be deprived of current though?
Yes, which is why all parts of your circuit need their own local supply filters. To ensure they are private
reserves, it is sometimes necessary to isolate them from each other. Since your low-power loads will have fairly consistent (and low) demands for current, one method is to keep its voltage supply at a higher impedance than the battery. As also mentioned, another technique is to bulk up on capacitance such that the startup draw of the high-power load is entirely satisfied by local capacitance. Of course, then the caps need to recharge, so some PSU isolation may be warranted anyway. IMO, you're on the right track using inductors. They provide high resistance during surges and low resistance during idle times -- perfect for allowing local supply caps to do their jobs.