I'd definitely like to know too! I was watching a cake challenge on Food Network and I couldn't believe they were putting fondant in the refrigerator. I thought it was an absolute no no!
I have read here on CC that it is okay, but it helps if you have the cake in an air conditioned room when you take it out, or put it in front of a fan to deal with the condensation as it comes to room temperature.
If you have any gumpaste or fondant flowers or other decoration on the cake, that could be a problem, though... Melting of the gumpaste or bleeding of colours.
This has been addressed many times and you'll get a lot of different views. I put all of my cakes in the fridge....always atleast overnight and sometimes for a couple of days. I've used Wilton & Satin Ice with absolutely NO problems.
I put fondant cakes in the fridge all the time with no issues. I live in FL, and it gets REALLY hot and humid here. My home is, of course, AC'd 24x7, but I really don't keep it that low. Better cakes suffer than me 
That said, the only time I have seen sweat from a confection of mine was on RI deco's I put in the fridge. I was careful and fanned them when I took the cake out for pick up, and the colors did not bleed (thankfully) 
I have put fondant cakes in the fridge and freezer and never had any problems. Airtight is a definite plus. The only problem I have ever had was when I put fondant flowers or other decorations in the fridge. Mine wilt. But a fondant covered cake has always came out in perfect shape out of the fridge. If there is condensation, I just let it stand until the condensation evaporates.
I always put my mmf covered wedding cakes in the fridge, I have to since they are filled with mousse fillings (with whipped cream in it). They usually sweat a lot when I take them out... no matter what the weather is. Put them back in the fridge and the dry up fast. I have tried to put them in cardboard boxes, or plastic, but they still sweat all the same. It is so sad to deliver a cake that is shiny and sticky, but I don't know what to do. I will try the fan idea and see if it helps. I use the "Rhonda's Ultimate MMF" recipe from here.
Is anyone able to put mmf-cakes in the fridge without the sweating?? Please let us know the trick if you do!!
lanibird, do you mean that if they stay at room temperature for a while they will dry up again? Mabye I havn't left mine out long enough, but I'm always scared the whipped cream will go bad. I try to get it out of the fridge at the very last moment and the deliver it right away.
Well, as said before, mabye the fan idea will help to speed up the process. Or will it start to sweat again when the fan is turned of?
Yep, after a litte while the condensation will evaporate off and it will be dry. When I did the "Camp Rock" cake in my photos, I had stored the covered, but not yet decorated cakes in my fridge. The fondant on the 12" round was pretty much dry in about 20-30 minutes. Admittedly it was June here in El Paso, and around 100 degrees at the time I was decorating the cake.
HTH 
I always use perishable fillings and all my cakes go in the fridge. I use MMF and have put a cake with MMF, wilton fondant, butter cream, and fondant + gum-tex decorations in the refrigerator overnight with no problems. I do have a fridge just for cakes, and keep it a little less cold than normal, and I recommend letting the cake come to room temp. in A/C if possible before serving.
Hope this helps!
I put every single fondant cake in the fridge, even painted ones, every time, for at least over night, unboxed (it's an empty fridge though, just for cakes). They're always fine.
I take them from the fridge, to the cake box, to the car, to the wedding, and they're always fine. Really.
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