I fail to understand how blocking cookies on websites you have never visited before is harmful to "innovation", "education", "entertainment", "entrepreneurship", and "millions of consumers". Cookies exist as a mechanism for websites to store data. They're used to keep you logged into your Facebook, Google, Twitter accounts. They've have gotten bad reputation over the years due to the ability for arbitrary websites to set them as tracking information. Mozilla's decision here helps retain the original purpose of cookies. Sites you have never visited before have no business leaving session data on your computer. It is just illogical.

Additionally, blocking arbitrary cookies doesn't hinder advertising at all. Nothing in iab's entire letter even made the slightest bit of sense. The entire thing is filled with awkward phrases and confusing reasons that don't tie together. It wouldn't be a stretch to say the entire thing is written to confuse the reader. I'm disappointing this is on the front page. :(