Ask HN: Database scaling for credit card companies

All,

I've got a particular interest in database scaling. I'm familiar with the standard techniques taken by web2.0 companies/ facebook/ myspace / etc. However, I'm curious what the big boys, like the major credit card companies, do. Or bank ATM networks -- what kind of scaling do they have so that they can keep everything sync'd in realtime?

When you read scaling stories (I'm thinking about a digg conference presentation I saw) about web2.0, they talk about having soft synchronization -- that it isn't 100% mission critical to have everything updated in real time, in every single slave db server. But that can't happen in financial institutions.

Does anybody here have any insight into what kind of techniques and technologies the big (enterprise) boys use?