Have a few days to read stuff? Run over to NLOC and run a search for PCV. You will find *TONS* of discussion, debate, input, engineering, etc. on the topic. You will have a migrane when done, and still no straight answers. Even from Ford engineers.
It could be crappy rings, it could be lack of sufficient baffling, some people think it's by design to lube the blower rotors, but whatever the reason, the PCV in our motors vents too much oil mist.
You will find pics on NLOC of intercoolers *coated* in oil, as was mine when I pulled it off this summer. I was injesting about a half quart of oil per oil change through my intake. It was leaking out of the throttle body, down my intake boot, and out of my air filter.
I took mine to Ford for diagnosis, they ran a full compression check (so they said), etc., printed me out the TSB explaining that some oil injestion was "expected" and sent me on my way.
The common fix is to install a separator on the hi pressure side (the passenger side for the 5.4) to filter most of the oil. There are some really nice ones that people are using on NLOC. The Wal-mart $20 ones do not work as well, but might be sufficient for the flow in the 4.6.
Others, like me, ripped the whole system out and use breathers. You're supposed to get a retune for the change in crankcase pressure, but it hasn't caused me any problems yet (I also made sure to seal off the system properly though). The only problem now is that the oil runs out of the breathers and down the side of the engine rather than through the intercooler.