The NY Times Deal Professor column did a post-mortem on the disastrous 2000 sale of speech-recognition company Dragon Systems to the Belgian firm Lernout and Hauspie. Not least of the problems that resulted was Lernout's collapse as a result of accounting fraud. The long and the short of the story is that the founders of Dragon, James and Janet Baker, ended up losing their entire investment in Dragon and spending the last dozen years suing those they felt responsible.
Last on the list was their advisor, Goldman Sachs. The Bakers sued Goldman for negligence and providing misleading advice. In a verdict announced on January 23, Goldman prevailed in this case, with the jury agreeing that their liability was limited because they were merely presenting "advice and assistance," not guaranteeing Lernout's suitability as a buyer. And the firm was successful in painting the Bakers as eager to close the deal quickly, to reap a windfall and, perhaps, to rescue their company from its own financial problems. In the end, the jury decided that the Bakers were responsible for the transaction and its aftermath.
The biggest lesson I would draw from this fiasco is that you can't hire someone to act in your best interests. Anyone you hire will act in their own interests, and the best you can hope for is that your interests and your advisor's are somewhat aligned. The only one who can act in your best interests is you.