Just as well for the WWF that the mills churning out these non-essential shirts got their order in before Earth Hour shut them down. Cost? Thirty bucks. Add another $20 for delivery outside Australia.

The profit margins in this literal black market are fantastic. When life hands you darkness, make dollars.

It's almost worth buying one just to see if it arrives in a plastic bag.

According to Peter Garrett, the Federal Minister for Periodic Bag-Related Statements, everybody agrees that having 4 billion plastic bags floating around Australia is not desirable.

Well, we aren't in a position to know. We've never seen this phenomenon.

It could be kind of attractive, like a big Christo Australia.

Plastic bags float around the environment in a similar way to Midnight Oil records and CDs. That is to say, they don't.

They get used and reused until they eventually get thrown out in the garbage and become stable and non-floating landfill.

Again, like Midnight Oil CDs. Three million of those are loose in the environment. They probably kill dolphins - if you throw them hard enough.

The profiteering theory of environmentalism might not seem to apply in the case of plastic bags.

The minimum-wage workers who make them don't earn enough to blow $30 on an anti-electricity T-shirt and banning or restricting them doesn't appear a likely path to riches.

But look closer. At Borders books they now hit you for 10c per bag - presumably something of a mark-up on the wholesale price paid by the bookseller.