Finger-in-the-air time. On-demand DVD sales will reach $33 million in the US and major European countries this year but grow to a whopping $1.1 billion by 2012, a new report from Screen Digest reckons. The analyst says high street retailers are struggling to stock an ever-growing number of titles but on-demand mechanisms will let them offer a wider, deeper range of material and even custom compilation discs. Amazon (NSDQ: AMZN) Unbox already offers burn-to-DVD movies (only for backup and not playback) and several more offer mail order services. Screen Digest says such online channels will be most popular over the next couple of years, followed by burn-on-demand technologies offered in high street stores. A third of on-demand DVD sales will have displaced traditional DVD spending. Worth noting, however, the Amazon Unbox team believes online DVD burning to be “not very good”, “can take hours”, “computationally intensive”, “somewhat burdensome” and hampered by copy protection concerns.