Eventually the lab is going to screw up sometime, and you'll lose a roll, or two, or three. Eventually you're going to misplace a roll or envelope of negs. But losing a roll here and there is nothing like the amount of images you'll lose in a hard drive crash (if that's where you are storing your images).
I thought about buying a DSLR just for wedding biz, but after seeing the weekly posts on photo.net about memory failing, I just got freaked out. I can imaging dealing with accidentally losing a roll, or even the lab frying one or two rolls, but the whole day of photography vanishing into silicon limbo is terrifying. The film equivalent is having your house burn down.
Just as the computer is an important part of digital photography, proper back up is also just as important. It does no good to burn all your kids' pics on a CD if 20 years from now the CD is no good or can't be opened (the film equivalent to leaving your negs in shoeboxes in the damp basement). When I get my first DSLR I'll be budgeting in professional storage services as part of the cost, just like I may need more RAM and hard drive space.
No doubt that this problem will be thoroughly taken care of in the future. As everything we do becomes digital, affordable, reliable digital back-up services will be included in your internet service, or something.