The only reason I could see it being "dangerous" is that the flat-file indexing structure would mean XMB could wind up being painfully slow to navigate if you have a gazillion videos and .mp3s and .jpgs and demos and so forth.

But it's not like the PS3 is going to explode or anything ...

With the massive amounts of reads and writes the PS3 as well as any other HDD has a high probability of failing. Just make sure you have a backup of any data you store on a device.

I didn't mean it to knock the PS3. Same goes for the XBOX 360 and your personal computer.

It is painful to use when you've got 1000's of mp3's on it, wish there was a better way to organise it.

I've used about 160Gb of my 320Gb drive now, but it does worry me if something goes wrong with the PS3, you can't get the data off the hard drive, and you can't plug the drive into a replacement PS3 without reformatting it unless you back it all up using the utility. Regular backups are essential.