I'd like to mention a problem with blocklists like this that you put into /etc/hosts. I've noticed that many sites trivially evade the blocklist by adding a redirect. I.e., if example.com is blocked, but it redirects to example.ru or example123.com or example.team, then it still works. The spammers and advertisers don't have to change all the existing links to example.com -- they simply need to add a new redirect every few weeks.
that's not how /etc/hosts works. the domain listed in /etc/hosts (example.com) will point to 0.0.0.0 (or 127.0.0.1)... you'll never even make it to the server so you won't get the redirect.
Oops, you're right. I discovered that it was my browser that was "helpfully" adding www in front of lots of domains I had blocked in /etc/hosts. For instance, if I blocked example.com, my browser would automatically try www.example.com (which might then redirect to something else entirely).
In my case, I'm using Firefox. I can stop this behavior by setting "browser.fixup.alternate.enabled" to "false" in about:config.
