When I use my N810 in my car, I have a friction mount on my dash to hold on to the N810. This works great, but sometimes if I'm accelerating and hit a bump, the mount moves. I've had it slide off the dash once, but I was quick enough to catch it. The centre, flat part of the friction mount is metal, and I was considering securing a magnet underneath my dash for some extra hold for the friction mount.

But I'm not sure if a magnet will have any negative effect on the N810. As far as I can tell from online searching, flash memory and touchscreens are safe from regular magnets. But the N810 is much more than that and I was wondering if anyone had any insight as to what effect, if any, a magnet will have on the N810.

(note: I don't plan on placing the N810 directly next to the magnet, or holding it on the dash with the magnet. The closest it should ever come in contact with it is how close it is when placed in the friction mount)

It should be OK...
I say this based on the fact that N800 leather cover sold by Nokia is attached to the back of the unit via a magnet...

I adapted this cover for my newish N810 and have experienced no ill effects with on and off use for close to 30 days now.

Well, the usual concern with computers and magnets is magnetic storage, and the N8x0 doesn't have any of that. As for other effects, changing magnetic fields do induce currents in conductors; a magnet on a leather case is not going to be strong enough to do anything bad, but with a more powerful magnet, there may be a possibility of it affecting the device. I'm speaking from a purely theoretical perspective here - I don't actually know much about the N8x0's hardware.

Of course it's only a theory Captain.

I'll go with the free market theory in that Nokia would not use a magnet of any size if a magnet risked a hardware fubar.

Also Nelson, YMMV and any advice from me lays all the risk on you.

I was thinking the same thing. Chances are the magnets shouldn't have an effect based on information I've read. I found some cheap ones I can buy that have a lifting strength of 3 lbs. I can always cut some pieces off to lower that if I need to.

It depends on how strong magnet You'll use.
I played with my wsod'ed n770 and very strong neodymium magnets - I've noticed that when I put the magnet near LCD's electronics - screen gets more/less messed.
All I can figure is saturation of coil's cores - it was permanent for some amount of time - then it faded away.
I didn't try to play with these magnets on my n810 since then.

Yeah, a strong magnet near an LCD screen will cause weird colors. I wouldn't worry about a magnet being used to hold a dashboard mount in place, though. You can always give it a shot and stop using it if you do see any ill effects. I don't think you can permanently damage the screen with brief exposure to the magnet, and I'm almost certain that you'll be able to immediately see if there's a problem. There won't be any non-visible damage that builds up over time.

You may also want to consider a suction-cup mount. Usually these have a smooth plastic disk which attaches to the dashboard with foam tape, for use where windshield mounts are undesirable (or illegal).

If you're really worried about it, you could stick the N810 in its dash mount holder, and attach that to the dash with magnets. :P

Note that this post applies only to the N810, my N800 has a magnet mounted inside of the battery door cover. A strong magnet could weaken that magnet and result in the unmounting of the internal SD memory card.

Actually, the N810 is in the Nokia supplied dash mount holder, which I then mounted to the friction mount
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I have no complaints with the mount, it works great. I've had it since April and its only moved while driving like 4 times. All while going over a larger than normal road bump. It even stayed still when I tested the 0-60 times using Carman.

Magnets are just there as an extra security. Or I can fool friends my placing some coins on the dash and they stay still.