I am wondering how many of you who work for LARGE companies have a network architecture that enforces the use of three-separate firewalls to get at the data. In other words:
\* Separation of external (internet) parties and a presentation tier by a firewall
\* Separation of presentation and application tier by a firewall
\* Separation of application and data tier by a firewall

In short: Public->Presentation->Application->Data (where each arrow is a firewall)

Here is my problem: I work for a very large US company (75K+ employees) where each environment seems to have a different number of segmentation firewalls. We wanted to standardize our firewall architecture, but:
1) We can't find any real material to justify the need for three firwalls (as opposed to, say, just a single perimeter firewall)
2) We can't qualify the value-add of three layers of firewalls.
3) We can't sort out if this should be an architecture for just internet facing apps, or for ALL applications/appliances/gear.

Any advice?