As long as you keep the guitars dusted and most importantly keep the strings wiped down, I don't think there should be any problem hanging them on a wall. I only own 3 guitars nowadays, an Ibanez JSM100, an EJ Strat and a Takamine Hirade,(I've thinned the herd quite a bit)but I feel better when they're tucked safely in their cases. If I leave them out the strings tend to get yucky.