If you use Google analytics you can clearly see from where your traffic is coming from or what is the source of your traffic. While referred clicks can bring small increase in traffic. Direct clicks bring traffic. According to latest changes in Google and Alexa. They have started identifying fake clicks.
As You can clearly see when you are sending traffic through a traffic website to the other user the website is actually getting your click through the traffic website and vice versa. So in both case the actual traffic is generated by the traffic website. It also gives clear ways for the search engines and alexa to see from where the actual traffic is coming.
Some websites announce that they will provide traffic anonymously. That is as bad because they do not reveal their source but it is clear that the traffic is coming from somebody else not you anonymously.