nybble

Something I've found to stop rust is a product called "Fluid Film" http://www.fluid-film.com/

Bought it once because I couldn't find WD-40 and was suprised by the results. When I had my 99 Corolla, I used it on the engine block and bolts (bolts were starting to rust) and within a week or so, after brushing it off, the rust was gone. Then I coated it again, and 6 months later still no rust. I also covered the door jams, etc with it, but hadn't had a rust problem yet. I did use it on a surface rust problem I had above the windshield, and it did appear to stop it.

Definitely worth a shot.

up_for_life

Only the driver side front door on my 07 is rusting at the joint where the outer skin and inner skin comes together, no other door is like this.
The rust showed up in 09, i haven't done anything to try and fix it.

nybble

My friend has an 08 LS that has this too, just on the Driver door, right at the bottom. So far nothing on my '10 LS. I'm going to try fluid film on the friend's 08 and see if that slows/stops it and prevents any further corrosion.