Rust at body panel join
 

I just noticed serious rust bubbles where the two rear driver side panels meet (See photo).
Does anyone else have this problem, do you think it is covered under warranty?

2004 Titanium Grey AT - cleaned and polished regularly.

OK,now how do I get a photo to appear here ?? I uploaded succesfully now it needs a URL ??

No, you shouldn't have that problem at your relatively young vehicle age. Presumably you're beyond the warranty period tho'. However it wouldn't hurt to have the dealer evaluate and pursue as a potential latent defect item. If worse comes to worst it's a fairly easy fix for a body shop or even DIY. Some wet & dry fine sandpapering, primer, and feather in the topcoat/clearcoat so you don't show a seamline. It's probably not so much rust/corrosion that you need an inhibitor, but that's another fairly easy procedure prior to paint.

Update - my local Mazda mechanic tells me this is not going to be covered by warranty because the rust is at a panel join (Salty water collecting place) and not in the flat panel itself (manufacturing problem).
So a design flaw, not a material flaw in his opinion - I tend to agree.
Am I going to get Mazda to pay up for a design flaw? - not likely.
He told me $500 to clean it up and re-paint this and two adjacent panels.