Is this the beginning of the great unravelling?Australian real estate and the glorified building societies that back it — sorry, our big banks — are on the turn.And the blame is being sheeted squarely at the tax changes announced in the May budget, which wound back some of the excesses that had helped drive a 25-year property market boom.Was it a bubble?Quite possibly And now the boot is on the other foot.Those with property, who have sat idly by and watched real estate values climb to extraordinary levels, are upset by the prospect that the salad days are over.Many had the quinella going: Go big on property and put the rest of your cash into shares in the banks which profited from fuelling the boom.Despite all the alarm, and the lurid headlines dominating the financial press, the current downturn is still relatively modest by even recent standards, although it has the potential to become a significant event.Deflating a property bubble takes quite some skill; something that has escaped almost every government or central bank that has ever attempted it.Think Japan in the post-80s boom