This question has been posed many times over the years. When they don't receive their most desired cards right away, a few subscribers have suspected that it's not totally random (supported by their statistically NON-significant anecdotal evidence), while Totem generally insists that it really is totally random. I may be naive, but I tend to believe Totem.
Some day soon I'm going to max out and own all the VGHD and DB cards (via randomly received subscriptions of course), so it really does not concern me.