And you think this article started the holy war? I believe I just saw another article on his about how you should do SQL sorting in PHP until you graduate to MySQL, or so claims Digg's former architect.
The specific case -- IIRC -- Digg mentioned was a query which required MySQL to generate a temporary table too large to sit in memory, so it ended up being done on disk. Moving some of the processing out of the DB query and into PHP avoided that, understandably resulting in a huge performance difference (in-memory versus on-disk has a way of doing that...).