A while back Warner Bros. offered an opportunity to essentially trade in HD DVD versions of their movies for Blu-ray copies. In that case they were charging $5 per movie and it was meant as a nice gesture to those who had invested in the now dead format.
Now WB is doing something similar with DVD2Blu which will allow for people to send in their regular DVDs and for $7.95-9.95 can receive the Blu-ray version instead. There are currently 55 eligible titles with more likely to be added over time and orders of over $25 receive free shipping. In this case WB is hoping to make the idea of shifting from DVD to Blu-ray more attractive with an option to start converting libraries without having to buy every movie over again.
This makes for a nice option for those who have upgraded to Blu-ray. There are more than a few movies I would rather have on Blu-ray but don’t have the desire to spend the $20+ on. The majority of people though likely prefer their DVD collection. Until Blu-ray players see higher saturation in the market DVDs remain more convenient and accessible to own.