For the Cork industry's take on this, see
www.realcork.org
I read somewhere in the not too distant past that there was a shortage of cork, but after reading most of the above, it looks like it is more likely that with increasing population comes increased wine consumption, increased demand for cork, and that the amount of quality cork is being more difficult to find, driving price per bottle up. This looks to be a natural result of the rarity of growing places for the cork oak groves, causing a natural oligopoly to arise - making real cork progressively more rare/expensive.
Since most of us want more wine/more choices, and we are voting with our money to buy less costly but better wines, the manufacturers are responding with innovative packaging that will preserve the taste just long enough to get it to us, while making the overall process costs lower.
From my reading of the above site, it looks clear that I should now be able to assess what the manufacturer intended for the wines by the quality of the cork used, and to not keep aging a wine that was not meant to age, but rather to be enjoyed soon after purchase.
Goody! I will get to drink a few bottles sooner than planned! Hope none of them are already spoiled.
I have not found a comparitive article on the merits/problems of the various materials, but I would believe that some of the new plastic corks are as good or maybe better than Cork, and I don't think I would trust rubber to be taste neutral or as long lasting as plastic...I just wonder if the plastics used are TOTALLY non-soluble in wine over the long haul. Who knows, there may be wines that have been impossible to age over really long periods with the traditional Cork that will, in years to come become available, with Plastic stoppers!