Found that my driver door weatherstrip was torn at the seam at the bottom of the door jamb.
Apparently water has been getting past the rubber strip for a while (truck is an 08 Suburban with 97k miles) and now there is rust on the jamb beneath the the weatherstripping on the sill.
Told by the dealer water collects in this spot on all trucks (Suburban, Tahoe, Silverado etc) the factory places the one seam for the one piece weatherstrip right at the point where water collects and where the most foot traffic from getting in and out of the truck is.
Lesson here is to check this spot and change out the worn weatherstripping before water damage occurs.
The cost of the weather strip for the door is $90.
Need to seal the joint so water will not penetrate.

 

Great information!
Can you post a picture of the area in question?

 

As requested.

 

Another shot.

 

One more.

 

I do see a little ware on mine it that area also... I have been applying 3M silicone paste to mine to help keep all the weather strips in good shape, but it won't protect from repeated foot traffic...
Thanks for the pictures, that should help others pinpoint exactly where to look for concerns before they start!

 

And don't drag feet across the threshold.

 

I keep mine too clean for that. 81,000 miles on 09.

 

Mine is showroom condition always.
The issue is the poor design and placement of the weatherstrip seam located at a point where most traffic is getting in an out of the truck.

 

Since there doesn't seem to be any scuff marks on the adjacent plastic or the aluminum inlay, I'm at a loss at to just exactly what's causing this wear. Is it only on the driver's door?