Cactus Music
I find it hard to swallow that any file format becomes corrupt if saved to a normal hard drive. Over the internet of course that's different. These people have all saved their work as a bundle on a hard drive, CD/DVD ROM or USB stick only to find they cannot open it latter down the road or at their friends house. Why?
Because all those storage media are capable of dropping bits. When you format a hard drive, it marks off the bad sectors and won't let you write to them. However, there's no guarantee additional blocks won't go bad over time. The surface of a hard disk is not immune to old age.
Flash RAM can lose cells. In fact flash memory has fairly complex data management schemes to avoid writing to the same areas over and over again, which wears the cells out and eventually causes failures. Optical disks are subject to a variety of problems, especially if stored incorrectly. CD-ROMs have had pinholes in the aluminum, and various other issues such as exposure to heat or ultraviolet light can corrupt data. Production runs of cheap optical discs can be bad and you won't know it until you try to retrieve a file years later. Blu-Rays are probably the most robust of the optical media but when you're storing 25 to 50GB on a disc, that's a lot to lose if there's a problem.
This is why I don't just save multiple times, I save to different media if possible. I also use offsite storage. I just gave 135GB of video backups on Blu-Ray to a friend who's involved in the company for whom I made the videos.
The only reason people freak about bun files, or zip files for that matter, is if one little thing goes wrong you can't recover the data. As a result, it's not the best choice for long-term storage. But it's a great choice for exchanging projects over the web. Right tool for the right job, and all that.