In the late 1990s and early 2000s, the religious extremists in the Taliban government cracked down on all un-Islamic parts of Afghan society, banning television among other things. This crackdown eventually led to the declaration the monumental statues as un-Islamic. In March of 2001, in a shadow of perhaps what was to come later in September of that year, the Taliban government in Afghanistan ordered the Buddhas to be destroyed. It took almost a month, since the statues were carved directly into the mountain, but eventually, after repeated barrages of artillery fire, and other methods, the Buddhas were destroyed.
The condemnation of the act by the Taliban from the international community, was, as you might have guessed, universal. I believe that the human race lost a priceless piece of its heritage when the Taliban made that deplorable decision. On a positive note, since the Taliban government was overthrown, there have been plans to rebuild the monuments.
An old photo showing one of the Buddha's before it was destroyed:

During one of the barrages that eventually destroyed the Buddhas:


