This is pretty interesting but if you think about it it kind of makes sense. The larger companies probably have a lot more data intensive tasks and probably account for dozens of startups.
It's surprising that it is banks though, not really sure what they are using AWS for and how they are handling privacy issues.
A comment on the post also mentions a good point: AWS presents a much better cost savings to a big company vs a small one so it's a no brainer that they are using AWS.
There are lots of back-office and internal systems that could use something like AWS. For instance, statical analysis of individuals and their chance of defaulting a loan. Or using their past cash flow to determine how likely the person is to buy a specific product, and offer the most likely product at the ATM.
I believe a lot of early stage startups were not jumping on board EC2 because up until now, it was only possible to use it to augment existing infrastructure. Big companies can afford to have their main data centre and the AWS stuff. A lot of early stage startups can only afford their main data centre (or in some cases main hosted solutions). Not only that, a lot of early startups don't need to augment their main infrastructure as there is no demand for it.
I spoke to a lot of friends and acquaintances in smaller companies and startups that all said the same thing: "once EC2 supports static-IPs we'll use it". Now that EC2 has Elastic IPs, I'm sure using EC2 for the main set of servers will be an attractive option to startups and smaller companies.
Banks and other financial institutions do a lot of 'risk management' -- that is calculating huge price correlation matrices on everything they have on their books.
This activity is perfect for AWS (and mostly pointless for its original purpose, as Citibank and others have proven).
I doubt that Citi uses AWS for anything... their auditing requirements are extremely strict about using any external services. When I was there (CitiMortgage, 2006) all of the heavy lifting was done on Big Iron IBM hardware.
Good news for those of us who'd like to use AWS as an option for our own corporate customers. Would be nice to have a reference list so we can say, "Even XYZ trusts AWS, so should you."
It's surprising that it is banks though, not really sure what they are using AWS for and how they are handling privacy issues.
A comment on the post also mentions a good point: AWS presents a much better cost savings to a big company vs a small one so it's a no brainer that they are using AWS.