Revver uses embedded ads to track hits on their videos, similar (sort of) to using an invisible image and counting the number of times it has been loaded. I do

Revver uses embedded ads to track hits on their videos, similar (sort of) to using an invisible image and counting the number of times it has been loaded. I don't specifically know about VideoCounter, for everything the uninformative article says they could be screenscraping/using public APIs to just grab the image views and using a highly complex summation funtion (typically represented using a plus sign).