Are screw caps breathable?

With the rapid swing to screw caps (which I love), is the myth of laying bottles of red wine down to allow them to breathe through the wetted corks going to disappear? Or will we be told that these are ‘special’ screw caps designed to allow heavy breathing? 

Actually, the tradition of laying bottles down on their sides to keep the corks wet is to prevent the wine breathing, not to allow it to breathe. If the bottle is stored upright the cork will dry out over time and shrink slightly. This will allow air to enter the bottle past the sides of the dry cork. A bottle laid on its side keeps the cork wet and prevents shrinkage. When excess air is allowed to reach the wine it can cause oxidation and give the wine a slightly tired, burnt flavour. Screw caps do not allow oxygen into the bottle, so you can store the bottles upright if you want to. You probably have storage space designed for flat bottle storage anyway, so you may as well use it. It certainly won’t harm the screw-capped wine.