Interesting article about map cases as I thought folks in the USA would want to ensure that they don't get soggy maps as well when venturing into the wider areas of true wilderness. I was a little surprised with the end of the following quote;
They’re also very handy in places where it rains all the time and where maps printed on waterproof paper are less available, which explains their popularity in England, Scotland, and many other countries of the world that still print maps on paper.
Have commercial printed paper maps gone out of fashion in the USA?
I also was rather surprised at some of the comments in the article, for example according to "Section Hiker":
"I reckon you see less map cases in the US because most hikers here hike in in areas with well marked, blazed, or signed trail systems. Heck some people even hike the Appalachian Trail without maps, although I still carry mine beause I like taking detours to scenic viewpoints. But US hikers hike almost exclusively....where trail systems are well managed and easy to follow....."
I reckon that Mr Section Hiker has obviously never been to Alaska! While we have a few "well marked, blazed, or signed" trails, more often than not trails around here are obscure, steep, with very little (if any) maintenence. It also has been known to rain around these parts, now and then.

For hiking I usually just carry my maps in a large zip lock freezer bag in my pack. If think I'll need to refer to maps often, I will print a small key section (using National Geograpic Topo!) on water resistant paper, put it in a smaller zip lock, and carry it in my shirt pocket.
I do have a nice fancy map case that I carry on the fore deck of my sea kayak. However in that case I usually have several items in it such as topo maps, nautical charts, tide books etc.