Trying to think seriously aboout this (although I'm not sure why :shock: ), I would tend towards the arc theory as Chris suggests as being the main culprit for tripping domestic circuit breakers when an incandescent lamp filament goes open circuit. From what I can remember of electrical theory, it is all down to ionisation of the gas within the lamp:-
When a tungsten filament lamp blows, it will tend to be just one spot of the filament that disintegrates and this forms a very very small gap betwen the two broken ends. Although the lamp will have been evacuated, there is till some gas inside the "bulb" - often argon (which is a "Noble" gas or inert element and usually a very good electrical and heat insulator). The voltage diffrence between the two points is enough to cause dielectric breakdown of the gas. This means that the gas atoms become ionised. When gas is ionised the atoms or particles become positively or negatively charged. This allows electron flow between atoms. In short the the gas becomes highly conductive. This current flowing through this ionised gas is better known as an arc or spark.
You then get into a sort of vicious cycle where more heat is generated and more energy is then devoted to ionising more gas aound the initial arc. The arc then grows, all the time reducing the resistance of the lamp, casing more current to be drawn and more heat and more ionisation and more arcing. So, as Chris says, you effectively get a "short" within the lamp which will cause it to momentarily draw maybe hundreds or thousands of amps.
Of course, this all happens in a fraction of a second and it's why you get a bright blue flash before your lamp "blows" and the breaker trips. Which is just as well because your 1 or 1.5mm sq cable that is used on domestic lighting circuits would soon start to melt with a few hundred amps going through it.
Posh incandesecnt lamps used to have little fuses built in them to stop the breakers tripping or fuses blowing. However, I suspect the dwindling stock of cheapo lamps that are left don't - they don't last long and are more likley to trip your breaker.