As part of our long-standing effort to keep YouTube authentic and full of meaningful interactions, we’ve begun periodically auditing the views a video has received. While in the past we would scan views for spam immediately after they occurred, starting today we will periodically validate the video’s view count, removing fraudulent views as new evidence comes to light. Google's YouTube to Monitor For Fraudulent Views [googleonlinesecurity.blogspot.com]

As YouTube creators, we ask you to be extra careful when working with third-party marketing firms; unfortunately some of them will sell you fake views.