My magnet has fallen off my stand on the back of the N900. This has made my camera go haywire, and not working sometimes. I could live without the magnet but not if its going to create these issues. Has anyone had their back cover replaced by Nokia warranty? (It should be imo.)

If I were you, I'd just contact Nokia's customer support directly.

As far as the reason why, I'm pretty sure there's a magnet-triggered switch somewhere on the back (similar to the N800's back cover magnet-switch).

I had the same problem. Nokia Customer support laughed at me essentially and told me to return the phone to my supplier. Very douchbaggish response. Anyway, that stupid magnet not only holds the stand shut, but its the magnetic switch thats used to determine when teh cover is on. This means that without it, the camera won't activate via the slide alone, and your SDHC cards wont mount. I fixed mine by buying some magnetic tape from Radioshack and cutting a tiny piece and gluing it in that little hole. Works perfect again, however my slider is also borked. The spring broke. I am a little saddened by the build quality of the N900s back in general. The rest of the phone seems pretty solid, but I strongly suggest that after you get that fixed, you take better care of the phone, treating it like an unboiled egg

I'm actually saddened by the build quality of the N900 itself. I could drop the N800 repeatedly, and come out with a couple scuff marks, nothing major.

Although, this is to be expected with so many movable parts (particularly the screen).

Back on topic, chrisp7, this would be your solution, I guess.