The only hard evidence I've seen that the Sony's display has glass elements is the photos of ones whose screens
have been damaged by physical trauma -- they look like broken glass, not broken plastic.
The other displays we've seen that are flexible and very definitely plastic aren't technically e-ink -- they're other forms of electrophoretic displays that are made with technology other than the approach that e-ink pioneered (with the exception of some of Phillips' efforts). They are also, every single one of them, not yet commercially viable products, so I don't give their existence much weight in the current discussion.
