Besides, Justin get's more RTs than Gaga, his fans are more active, more relentless, trend more topics for him etc. This is silly. Just use common sense and you can obviously tell that Justin is bigger on Twitter than Gaga.
And the other post was based on this http://fakers.statuspeople.com/ Obviously you're going to go with this source since it works in her favor, but you can't claim one source above the other since Huffington used both.
Either way, there's no real way to determine who has the most fake followers.
Statista is WAY MORE reliable than fakers.statuspeople
Katy has more fake followers than Gaga, deal.
...some people
