What if this service stops to exist after 2 years? Then any place you advertised/published this subdomain will need to be updated. With your own domain you won't have that issue, ever. Why would you give that up?
I just got an email from Twitter explaining that there was a bug in the password reset system, causing active sessions to stay active after a password reset.
While I appreciate the approach of making "the world" a bit better once you see a chance to do so, I also don't think a company like Google should (be able to) leave it to random internet users to clean up their mess.
I tried the report abuse button and got a 404 when submitting the form. Lol, classic Google.
EDIT: My guess is they delisted the extension right about as I was submitting, since the extension page loaded, but the report submission failed, and now the extension is also gone. Maybe a cache purge was in there somewhere.
I reported abuse few minutes back. Google pulled it out shortly after that.
Also I am pretty sure Google has a "karma" number for users (just like reddit) in the backend where they automatically take down if report is from a user with high karma.