There's also the fact that when Amazon and Google have failures, those failures are public. They affect a large number of consumers and they're widely reported.

There's also the fact that when Amazon and Google have failures, those failures are public. They affect a large number of consumers and they're widely reported. If a Merril Lynch internal system goes down and costs the company $10 million, is it going to get reported? Will there be a public post-mortem that you can cite? Probably not. Companies of all sorts, especially financial companies, don't like airing their dirty laundry in public and will only do so when there is significant market or regulatory pressure to do so. So who knows if Merrill Lynch, Morgan Stanley or Goldman Sachs' networks are as reliable as Amazon's or Google's? I don't see any of the former companies admitting to serious network events, much less posting public post-mortems that detail what, exactly, went wrong.