A few common questions have come in so I wanted to provide a bit more detail (and a few pictures) to help.
Common Question #1) Are the bags waterproof?
Both fabrics on the ChipmunkBag (1000d and 420d) are water resistant. Water will bead up on the bag and keep the interior dry for a while. The bag will be fine if you're going a few blocks in the rain and need to keep your laundry dry.
Common Question #2) Do the bags stand up on their own?
The bags stand on their own when about half full. We've considered adding more structure to the bag, but decided against it. Part of the CMB's benefit is it can squeeze into small areas like an overhead compartment on an airplane. This would be harder with a wireframe structure built into the bag.
That being said, the bag still functions as a hamper. I have a small adhesive hook in my closet at the same height as the bag's hanging handle. All I do is loop the handle over the small hook which keeps the bag upright until it's full enough to do so itself. On laundry day, just grab the CMB and go. No need to transfer clothes from hamper to laundry bag.
I updated the FAQ section on the page with these questions. As always, feel free to shoot me a message if you have any others - happy to help!