He talks about Facebook, it's valuation in this pre-IPO period, and the likely unsustainable valuation of the company. He also talks a little about the potential conflict of interests for the myriad of roles Goldman Sachs could play as the exclusive I-bank for Facebook (and likely Mr. Zuckerberg). If Goldman Sachs wins from this deal, who loses? "The average investor, of course, who will get stuck holding the bag when, someday, Wall Street realizes the firm's financial performance doesn't lived up to its hyped valuation."
Perhaps unethical was the wrong word, but this seems like the worst of the markets at work in a lot of different ways.