One of the Tom's Hardware System Builder's Marathon Builds had issues supposedly caused by the Noctua NH-D14's weight, but this was the exception, not the rule.
The main worry about the extra weight on the motherboard is to be careful when transporting your CPU - and the same rule can apply to video cards. They can be quite heavy as well.
If the weight was a truly serious problem, there wouldn't be a market for the product.