I have to say I've never seen a photo of what you could term a "self-illuminating" orb. I've seen plenty of what could be termed "light anomalies" when out at locations, although I could never say for sure whether these are down to either suggestion or some optical issue rather than spirit communication.

I suppose an important consideration is that a number of well recorded paranormal experiences have featured some form of light anomaly or similar. Jenny Randles' description of an incident on Cannock Chase springs immediately to mind.

As Mysteryshopper says, what's fascinating is why such a mundane (and nowadays easily understood as mundane) thing as orbs have become so heavily associated with the modern mainstream view on the paranormal. Scary how a hammy cable TV show can have such a big effect, eh?

I cant see how a lightbulb is self illuminating as it needs an external source of energy to operate.