Basically, there are at least 3 standards for digital 3D: RealD, Dolby 3D, and XpanD. Most theaters have gone with RealD, mostly because the glasses are cheaper, and are usually recycled or disposed of by movie patrons, and that is what Kevin's original post was referring to.
Dolby 3D and XpanD are infintely more expensive, thus theater owners tend to want to make sure they do not go home with patrons.
RealD Glasses (passive)
Dolby 3D glasses (passive)
XpanD glasses (active-shutter)
Dolby 3D and XpanD are infintely more expensive, thus theater owners tend to want to make sure they do not go home with patrons.
RealD Glasses (passive)
Dolby 3D glasses (passive)
XpanD glasses (active-shutter)