Vertical component placement?

 It seems as though rather than the previous standard 17-19” components, there are more and more small boxes in hi-fi these days. Perhaps, it’s just a product of audiophile OCD, but I find stacking equipment directly on top of each other an anathema. It occurred to me that if placed these small boxes vertically on their sides, I could maximize available shelf space. Would there be a down side (pardon the pun) to equipment, as pertains to ventilation, circuit board component integrity, or anything else for that matter in doing so ?