How dangerous is it to hot-plug FireWire 400 devices? I've had my MacBook since 2006 and, on the odd occasion, I've used the FireWire 400 port for connecting an HDD caddy or for networking between two Macs. I've always hot-swapped devices without a worry. I've always assumed that's what FireWire was designed to do.

However, recently I purchased an M-Audio ProFire 610 - it's a multi-channel digital audio interface - and plastered all over its documentation (and the website) are warnings that you MUST turn the device off before plugging or unplugging. I was quite surprised by this, and wondered if it had anything to do with the device being dodgy.

http://forums.m-audio.com/showthread.php?17235

Apparently then, this is not an issue with M-Audio devices, but with ALL FW400 devices... Although it's the first I've ever heard about it, which I find a bit odd... If there really is such a fundamental flaw in FW400, why wouldn't I have heard people complaining on Mac forums about fried FireWire controller chips?

Is it dangerous in general, or do you think that perhaps M-Audio are trying to cover-up for shoddy manufacturing? Like I said I've never had any problems hot-plugging FW devices before and now I'm really paranoid, turning the computer off every time, which is really frustrating.

Not only that, but supposedly the issue is power arcing onto the data pin... But if you power down any Mac device (MacBooks included), they still deliver power to the FW device. So how safe does powering it down really make it anyway?
The issue is not with M-Audio or with the firewire standard, but with a oxford bridge controller design flaw which makes the controller susceptible to power spikes.  

The flawed chip was in a lot of computers in the late 2000s, which means that it was a good call for m-audio to issue the warning.  It wasn't their own butts they were covering, but it did mean a lot of down time and troubleshooting for their customers.

I learned this the hard way, as the firewire 400 port on my old macbook was fried by hot-swapping the pro-fire 2626.