Nah- it easily folds forward to allow access to the underdeck storage area. I bought the Toyota one which is quite rubbery with very little lip. On my '96 4Runner I bought a Husky cargo liner, and while tough, it was quite plastic-y feeling although it did have a nice 2" lip; the Toyota one is much more flexible. Quite happy with it.
On ebay, another type of cargo mat is always up for auction; it looks intriguing because it seems hinged and folds down for some protection when the 2nd row seats are folded forward. Here's the link:
I have that mat. It is really easy to lift up as it's very light weight. Looks to be made of some foam type material that is resistant to spills and such. Wasn't to sure about it in the beginning but I've thrown a ton of stuff back there on it and it's held up fine. The nice thing about it is it has little lipped sections that help stuff from sliding around...
Thanks! I decided to go with the Rubbertite cargo mat. It's more like the carpet mat, without a lip, and I think will be easier to maneuver. It has indentations to keep dirt and water in and it's only $59.