Ok, here's the deal with the fridge:
1. Cold, dark storage won't hurt ANY snuff. So it's entirely fine to store in the fridge if you want - provided you keep the tins closed up to avoid the scents from mingling, you're not doing any damage. For most of the big-brand snuffs, it's completely optional.
2. If you have any "artisan" snuffs, you should seriously consider keeping them chilled. Most of these aren't treated with any antimicrobial agents or preservatives - they will go stale or (worse) turn moldy over time. The fridge goes a VERY long way in retarding that process (it also helps to avoid pinching from the tin...keep your grubby mitts off the artisan stuff - use a clean snuff spoon or, better, transfer a bit to another snuff box and use that for pinching).
These precautions aren't entirely necessary if you know you're going to finish a tin within a few months of opening it, but if you're a "open some of this and some of that and get around to it whenever" kind of guy, or if its a tin that you might not open for a while, cold storage is strongly advised (the artisan blenders will tell you the same).
To that end, artisan brands that aren't heavily treated that should be stored cold include Old Mill (now defunct), Open Source Project, Sir Walter Scott, and Rozinsky. Abraxas maybe, but I'm not certain.