I would really hope that Dropbox doesn't supplant the role of traditional off-line backups. What's the point of having your data backed up to a web service that

I would really hope that Dropbox doesn't supplant the role of traditional off-line backups. What's the point of having your data backed up to a web service that can go offline, both temporarily and permanently? Off-line hard drive backups are also cheaper, since you aren't paying a recurring fee for the hardware and your drive is likely to last several years.