I can't believe you guy are complaining about developers including extras. Yeah not all developers will do it, or do a good job, but those that do a good job will make it something special.
Developers have been hitting the DVD barrier, Mark Rein has said as much, but it depends on the games. The reason you don't see devs including many extras on their games, typically is because they have already stacked the DVD fairly full, or they are lazy. In the first situation they don't have room for a full length 10 minute making of or what have you. Why do you think MGS3 Subsistence comes on two discs? Because they can't fit the main game+everything that's included on it and the multiplayer data on one DVD.
And heck, if I can get gimmick content that I would of otherwise had to pay an extra ten dollars for in a special edition, why not.
With not having to worry about space period, you can epect a lot of devs to just throw extras onto the disc, which suits me just fine.
And if they want to encode any of their stuff in HD, video wise for a making of or whatever, they're going to need that space.