There are distinctions to be made between rotating/static display ads, spam and everything (i.e., user surveillance) that encompasses digital advertising today. Personally, ads don't bother me. Spam is annoying in terms of UX. But really, user surveillance is what we need to worry about in terms of UX, our privacy, security, etc.

I think there's a worse-step beyond passive surveillance, where ad-networks function as a channel for viruses that seek to change your computer, along with scams and phishing.

Ad-blocking--refusing to run their code--is a simply common sense when the networks are not liable for ensuring that the code they send is not malicious.