The Berliner Philharmoniker are giving out free 48-hour tickets for the Digital Concert Hall, their on-demand video streaming service, for people who fill out a survey about the service. The ticket gives unlimited access to their concert recordings (or live-streamed performances) over the 48-hour period.
Once you have completed the survey, you will be given a coupon code which is valid until 31 March 2015.
As far as I know, the cheapest ticket you can normally get is €9.90 for a seven-day pass.
To try out the service, you can watch their free concert with Sir Simon Rattle and the orchestra performing Schumann's Symphony No.1 in B flat major and Brahms' Symphony No.1 in C minor. The 48 pass will give you access to all the live streams and concert archives.
Great find, thanks!