I've had several pieces stacked, without issue, but I find that now that I have a Patchbay, I don't have to stack them, or keep them close to each other.
A Patchbay is the single greatest (and cheap) investment I've ever made to my studio... I route everything through it now, and don't have to change wiring much anymore.
I like it so much that I got a MIDI patchbay as well, and use it similarly.
I agree that the trouble will come from either heat, or knocking stuff over.
I haven't knocked anything over (but I never went 8 high either), but I have some equipment that gets fairly hot over time, and I'm not comfortable stacking anything on top of it.
I would add that another thing that comes from having a patchbay is prolonged equipment life. Unplugging and replugging cables over and over and over isn't the greatest for the connectors. A patchbay will limit the long-term damage to the cheap patchbay, rather than the (presumably) more expensive equipment. And, patchbay connectors are generally engineered such that a user can switch them out easily. With the other gear, you'd likely have to pay someone to do it... much more expensive.
Take care,
- zevo
post edited by inmazevo - 2007/01/05 16:04:10