YouTube are crystal clear in their rules about this:
"Views generated by some third-party businesses and services will not be counted or reflected on YouTube, and can lead to disciplinary action against your account, including removal of the video or account suspension."
Source:
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And before anyone says "but these are real views" - No they're not. - Real views are views from people who found your channel all by themselves and genuinely want to watch your content, who will sub, like and comment and share etc and then come back for more.
Google employ some of the smartest engineers on the planet and their algorithms can easily detect artificial sub/view exchanges. ie lots of channels suddenly watching each other's videos. All you'd be achieving is at best seeing your view count increase artificially in the short term. But you wouldn't have gained any new fans and in the longer term, those views would probably be removed and quite possibly get your channel terminated.
