The phenomenon of people condemning vices they have indulged in themselves already, and since given up. Inspired by the _Confessions_ of Augustine (417 CE), in which Augustine describes his career path and then denouces the things he did to get to where he is.
WHY IT'S BAD
With SAS, the perpetrator has received the BENEFITS of a particular vice. It could consist of sleeping one's way to the top, or lying a lot, or getting divorced, or indulging a vice until it gets tiresome. At that point the perpetrator makes a big display out of quitting the vice and condemning it publicly. It's like climbing a ladder out of a ditch and then pulling the ladder up so others can't get out of the ditch; and to add insult to injury, the perpetrator ridicules the desire to use the ladder.
Like other forms of hypocrisy, it's destructive because it enforces stupid social codes. If the social codes were right all along, then the perpetrator should not get off the hook for violating them, but, in effect, he gets praise for having done so (and having "kicked the habit"). If the codes were wrong, then they should be confronted . And finally, it's bad because it creates a meritocracy of bullshit
A good example of St Augustine's Syndrome is Doctor Laura Schlessinger, the evangelical talk radio host who climbed her way to the top, divorced, and then renounced feminism. Many putative sages are famous for having had, earlier in their lives, immense amounts of sex with numerous partners, only to renounce the ways of the flesh and denounced materialistic society.