It means we can't trust people on the internet.
This should come as no surprise. Experienced internet users already know not to take things at face value, not to feed trolls, and not to take anyone's "word for it".
In civil, learned communities (like Slashdot, for example) a "shill" is fighting an uphill battle when trying to spread disinformation--anything that's posted here will be carefully examined.
Even in volatile, less-learned sites (4chan's /b/, for example), they'll still have to trudge through a hundred miles of skepticism and snark to convince any sizable demographic of any one thing.
I'm not saying "shills" can't be effective on the internet. I'm just saying I'm glad I don't have their job.