Most ripping erors are the fault of some alignment issue or in the simplest case dust on the DVD pickup lens. The dust accumulates on computer DVD drives because there is usually an air flow through the drive created by the cooling fans. Higher end DVD drives have a felt gasket that helps cut down on dust entering the drive.
I recently ripped my collection of DVDs to LinuxMCE, or at least the 80 or so that I feel are worth ripping. There were only three that wouldn't rip: Open Season, Madagascar and Pirates of the Caribbean.
I did have problems with one DVD drive and it had ripping failure with about a third of the disks.
It is presently illegal to rip disks. I am only ripping disks that I have purchased and have a legal right to use. I am still violating the law in that the DVD that I ripped can play on multiple machines at the same time in my house. I feel that the licence to use the media that I purchased gives me the right to do this. I can carry the disk from room to room and use on multiple machines, what I have done is to take it one step further and allow me a cleaner easier to use format for the licence I purchased.
The answer for the producers of the media is to only provide movies on blueray or HD DVD. We will then feel it is not econonomical to copy the 54 gig movies to our 500 gig HDs at 11 dollars a movie vs. our current $1.50 for the 480P DVD media.