Sorry to say it but they're going to be able to exclude whatever you throw at it.
And even if you found some way to meaningfully degrade the quality, they'll analyse what you do and find a solution for that.
They are not going to suddenly throw their hands up in the air and decide to give up.
It's a matter of how many resources can you throw at the problem and how many can they to counteract you.
This is just the Luddite fallacy repeated over and over. By this logic, we should never develop new informatic methodologies, we should never develop new forms of analysis, we should never develop new software – because of economies of scale exist.
I'll the state the obvious: that's stupid. There's no way to soften that blow.
How, exactly? You're talking about something that's one of the most poorly understand areas in AI at present, and making it sound like it's a solved problem.
With manpower. I said that they are going to analyse whatever users do to wilfully degrade the service and will find a way to exclude that.
Just like they do with search for years. Somehow they manage to keep their search relevant even though so many people constantly work on coming up with new SEO tricks that would seriously degrade this service if left unchecked.
Of course I cannot know how _exactly_ they will do that, even the persons working on that service cannot know at this moment how exactly they will keep this working in the future since they do not know yet what people will try to do.