Looks to me like a ballast failure there.
Magnetic ballasts tended (at least in the UK where they're simple due to our 230V mains - in the US, you'd need autotransformers to step the voltage up...so they're probably more complex and I imagine somewhat more temperamental), to be very reliable. The only failure mode was occasionally through overheating, which tended to lead to them going open circuit in a somewhat smelly but otherwise utterly undramatic manner.
Two problem failure modes in modern electronic CFL's.
Firstly being the ballast, which runs so hot (especially when run base up and/or in enclosed fixtures) that it usually ends up cooking one or more cheap electrolytic capacitors which aren't designed to take the heat - what happens then is hard to predict, varying from a dead lamp, to a flickering lamp, to a loud bang and potential flames. Decent lamps should have a casing made of flame retardant plastic that won't burn. I've TRIED to set fire to the casing of a decent Osram CFL with a blowtorch without success. A cheapo from Tesco (which I belive to be made by GE - don't quote me on that though as it's only a theory) however did burn, though it took a fair amount of starting. This tends to be a problem either in poorly designed higher power lamps, or very compact ones where no thought has been given to ballast cooling whatsoever. It's hard to get a sense of scale from that picture, but that looks like a 20W or so lamp there from the diameter of the spiral.
The second problematic failure mode is again down to the ballast. Even when an electrode has lost its emissive coating, a lot of modern electronic ballasts have the ability to provide sufficient voltage to still maintain a discharge. However the resulting higher voltage drop at the electrode in question means that there's a ridiculous amount of power being dissipated there compared to what it was designed to deal with. The vast majority of the time this will blow the filament open circuit, shutting down the lamp in pretty short order. Sometimes however that doesn't happen, resulting in tube end temperatures sufficiently high to soften or crack the glass. Or, theoretically melt the plastic around the base, though I've never seen it actually set fire to a lamp. It can however coax a ballast (which will be pretty well aged by that point) into failing, as it will be running at a higher tube voltage than it was designed for - the imbalance in electode voltage drops will also lead to a certain amount of rectification taking place, again - not good for the ballast.
A decent ballast should be designed in such a way as to "see" electronically when the emissive coating on an electrode has been exhausted, and shut the lamp down, especially given the trend for ever narrower tube diameters these days.
It's still scary to see things like this happening though! If that had been in a house, left on unattended and it fell onto a sofa or was next to a set of curtains, or even onto someone - the results just don't bear thinking about.
I'd be getting in touch with the manufactuer of the lamp if I were you. Certain environments don't mix well with CFLs either, if the barn in question is at all damp, that could well play a part, electronics and water don't generally play well together, for that reason the lamp in my parents shed is still an incan - I got fed up of CFLs fizzling out in the winter due to condensation.
