This totally happens. While the parmesan cheese adds saltiness, you also want regular salt to help break down all of the ingredients. So it's easy to overdo it a bit. If your pesto turns out a tad salty, just add 1-2 teaspoons of lemon juice and let is sit for a few minutes. The acid will offset the saltiness a bit, and letting it sit will mellow things out. With that said, if you are tossing the pesto with pasta or adding to a spread, a little extra salt won't be a problem!