Goldman Sachs is the Jekyll and Hyde of global banking

When the bank is good, it is very good. But the same can be said for when it is bad.

Lloyd Blankfein, the Goldman Sachs chief executive.

I've had this problem throughout my career in business journalism: whether to love or loathe Goldman Sachs.

When they're good, they're very good indeed. Goldman analysts tend to produce the highest quality research, make the most accurate predictions about business trends, and give the most insightful analysis of corporate situations. Because Goldman is at the centre of the financial world, you have to go to them for news and views.

And there is lots to admire in the sheer single-minded efficiency with which the bank pursues its goal of making money for itself, its employees and its customers. The way Goldman emerged unscathed from the 2008 financial crisis, when its rivals were being taken over, bailed out and merged, was awesome.

But simultaneously, there is the negative tug. For one thing, Goldman bankers and analysts are very snooty about whom they talk to. I contacted the managing director for the UAE this week to ask him about the role the bank was playing in the unification of the country's stock exchanges.

"I'm not authorised to comment, you'll have to go through London," was the robotic response. The MD is not authorised to comment? Whoever heard of such a thing?

That's one element of the "loathe" side of the equation. There is a whole stack of other things, too. While admiring how Goldman came sailing through the crisis, there's nothing to admire in the fact that they were at least partly responsible for it, by devising those wickedly complicated and ultimately valueless debt instruments in the first place.

Then, as Lloyd Blankfein, the bank's chairman and chief executive, was forced to concede before a belligerent US senate hearing, the bank made it worse by selling property-linked instruments to investors at the same time other parts of its business were dumping them. Not good for the image when that came out.

There was also the little matter of Greece. Poor, bust Greece called in Goldman in the early 2000s to advise it on how to meet the demands of the euro zone single currency, which the country was joining. Goldman came up with all sorts of wheezes - default swaps, credit derivatives, currency hedges - that did the trick for the Greeks and got them into the euro club.

But last year, the whole thing exploded in Greek faces when it turned out the cunning financial engineering constructed by Goldman had actually contributed to the country's deficit problems by masking the full extent of its real debts. The bank is being investigated for this in the US; its name is mud in Athens.

This week, we saw two prime examples of the "Jekyll and Hyde" nature of Goldman Sachs. In a deal with Facebook - everyone's favourite company - Goldman gave the social networking website its stamp of approval, and a potential valuation of US$50 billion (Dh183.65bn). That was either a masterful piece on investment vision, or a huge inflationary mistake that would prick the resurgent equity bubble, largely dependent on companies such as Facebook and the rest of the fashionable but profit-light "new communications" industry.

The other event was Goldman's cringe-worthy response to the criticism it has suffered over the past couple of years. Rolling Stone magazine had called it a "giant vampire squid wrapped round the face of humanity", and the bank hit back with a manifesto drawn up by a special committee of senior Goldman executives. "Our clients' interests always come first," it said, adding, "If we serve our clients, our own success will follow."

The document then went on to say sorry to all marine cephalopods everywhere for having given the squid community a bad name by being linked to Goldman.

No, it didn't do that, I made that last bit up. But such was the "sheer, toe-curling embarrassment" of the document, according to the Financial Times, and the "nonsense that fills 63 pages", according to the website The Huffington Post, that an apology to sea creatures as a whole would not have been out of place.

"Never trust anyone who has to remind himself about putting clients first. Because they don't, and they never will, based on the dopey prescriptions Goldman says it has now adopted to deal with a corporate culture that openly embraced sleaze in recent years," Huffington concluded.

The big problem for Goldman is this: it has made millionaires and billionaires out of employees and (some) clients by making investment banking an enclosed, secretive art-form to which you gained access only if you paid the big fees Goldman demanded. It cannot now open up with investors and regulators without giving away its secrets, and debasing the business model.

Which brings us back to the UAE. Goldman is advising the Abu Dhabi Government on how it might bring about a unification of the three stock exchanges in the country. No doubt there is a grand, sophisticated strategy at the heart of this, but we have yet to hear it.

At the every least, Dubai, home of two of the exchanges, needs its own independent advice on which to assess Goldman's conclusions, when they see the light of day.

Love or loathe Goldman Sachs, at least you have to challenge it.