A cork-y question

Made entirely of cork from Portugal, here's a bag that Stella McCartney would approve of.  The tag calls itself "durable as leather yet environmentally sustainable." I am curious though, is cork really a great green fashion option? Isn't there some concern regarding the limited supply of cork, with all these wine bottles starting to sport plastic caps instead? Is or isn't cork truly eco-friendly? I clearly need to do more research on this subject.