Google organizes the worlds information. Facebook does something that lots of people like (I guess). There is a vast difference between those and the banks in question. Banks should be run by accountants, doing boring accounting things, and being paid a fair wage for it. It should not be a license to extract trillions of dollars from taxpayers, without their consent or knowledge.
"Regardless, if banks are "concentrating wealth" they must be doing something right since after all, the ultimate purpose of a business is to make money. If they do so through illegal means (fraud, deception, etc.), we already have a legal system in place to deal with that."
You're not grasping the situation or what actions have been taken in this example, and with the crisis and bailouts in the US. These are banks setting the rates at which governments borrow money, and the rates at which banks receive money to lend. Manipulation of those rates is illegal, unethical, and highly profitable. It's been abused on a monumental scale, so much so that it has begun to appear "normal" to the people participating in it. But, despite being the norm, it's fraud on a massive scale, and it destroys wealth and robs taxpayers.
I'm not at all arguing that more government/bank interaction is the solution. But, as long as banks have access to all the levers in our economy, and the ability to borrow money at rates they control and lend it out to governments at market rates (a free money funnel for taxpayer dollars), there needs to be regulation of those banks. If you can convince our government to remove that intimate connection between creating money (not wealth; we're taking about the currency that represents debts) and lending money and the rates at which banks borrow money being introduced into the economy (i.e. end or dramatically rethink the Federal Reserve in the US, and figure out a way to resolve the fraud in LIBOR in the UK, and whatever equivalent there is for the Euro), I'll sign right on for your cause. Independent currencies, like Bitcoin, are something I have high hopes for, but the Bitcoin economy is measured in millions...it'll be decades before we have an alternative economy and an ability to opt out of the horribly broken state currency markets and into a free market currency.
In the short term, laws need to be upheld, in London, in the US, in the world markets. People who have committed fraud worth billions or trillions of dollars need to go to jail. Just because someone is rich, well-educated, and doing what everybody else in their industry is doing, doesn't mean they should get a pass.