EDIT: Ethical is a poor word choice here. Is it an acceptable practice for a consumer to bypass ads via Adblock?
I've heard both arguments:
EDIT: I'm sure there's more point of view but these are the ones that I've heard that seem to be popular.)
(Yes, it is.) I don't want those really intrusive adds plaguing my browsing. They're obnoxious. It's my browsing experience.
(No, it's not.) If you use Adblock you're depriving sites of ad revenue, which keeps them up and pays employee salaries.
Personally, I disable it on sites that I frequent and respect. The rest of the time it's left on.