Hosts files are a relatively obsolete way of blocking ads — it seems to be only because ad companies insist on serving ads and JS from their own domains. If a content site was sufficiently motivated enough, they'd serve ads exactly as content and include javascript within the content page itself to ensure they load.
Thankfully, I haven't seen anyone go "thermonuclear" on ad blockers yet except for executive-level decisions and lamentations — but as a technological-level problem it's theoretically straightforward to subvert given the rudimentary nature of ad blockers.