In 2009, the question of snus refrigeration really depends on who you talk to. Lets start with unopened cans and rolls of snus.
Many manufacturers of both Swedish and American pasteurized snus have made significant improvements on making the containers air-tight. When buying Swedish/Scandinavian snus by the roll, it also has an external plastic wrapping to further protect against air infiltration. If you're not going to use a roll right away, don't strip off the outside wrapper.
Two manufacturers; Swedish Match and R.J Reynolds do state their snus or SNUS should be refrigerated. It is marketed in coolers at retail by both companies.
Most other manufacturers and distributors of both Scandinavian and American snus say that refrigeration is not critical anymore but keeping a cool, constant temperature is. It's the same principle that applies to wine. Wide swings in temperature will destroy both wine and snus as will storing them in hot conditions.
Once you open a pasteurized snus, however, the situation changes. Many American pasteurized snuses only contain from 6 to 15 mini portions which are mild in both taste, duration, and nicotine; thus you will go through more of them quicker. I would not recommend leaving any snus, especially an open one, in a hot car for the afternoon. Walking around with it in your pocket is of little concern as you will go through these milder, short duration snuses within a day or so.
As to the Swedish and Scandinavian Snuses which do last multiple hours and come with usually 24 portions, I do put them back in the refrigerator at night or when I'm not using them. Once open, especially Swedish/Scandinavian Snus which has a much higher moisture level than American Snus will dry out; some quickly; once the can is open. Refrigerating open cans when not in use will help slow that process and prolong the taste and flavor or the snus.
As for myself, while I accept this on an intellectual level, I'm so used to storing Snus in either the refrigerator or freezer (for long term storage) that I just can't bring myself to put it in a drawer or on a shelf. I also like the taste of cold snus.
Please don't tell my wife as I am taking up a good portion of both our refrigerator and freezer with snus. She accepts that as the trade-off for me being able to finally give up cigarettes, but if she read this FAQ......lets just keep it between us.
Bottom line: if a manufacturer tells you their snus should be refrigerated, I wouldn't argue with them. If they don't or specifically say you don't have to refrigerate it, keep it a cool, stable temperature. And if like me, you want to refrigerate snus anyway, it won't hurt it.