I've flashed over a dozen Dell laptops, almost half of them Mini 10's, and have not had a problem with any yet. Over the years, between owning and working on various manufacturer's PCs, I've probably done a hundred BIOS updates without any incident of note. Some flashes are necessary to support new hardware, like higher density memory modules or newer CPUs, while others are general fixes of unspecified issues. While I'm not saying that every BIOS flash is safe, especially if done by impatient or unprepared users, the majority of them cause no ill effects. In fact, when you call in to Dell or other PC manufacturers for hardware/software support, one of the first things they often require is updating the BIOS and drivers to the most current versions.
That being said, some of what happens here is an exception because some users are trying to do something the Mini wasn't designed for, such as OSX or other hacks like downgrading so they can install OSX. Others are just plain bad luck I guess. Still whenever I get a new PC/laptop and anytime while it is still under warranty, I have no hesitations flashing the BIOS. Dell is especially easy to work with for warranty issues, so why not? About the only golden rules for BIOS flashing is to never lose power during the process, and being patient even if it looks like nothing is happening on the screen. That means having the battery fully charged or in the case of a desktop, plug it into a UPS.