D Squared advertised by sending pop-up ads using Windows Messenger (NOT MSN Messenger). Windows Messenger was originally made for administrators to send messages to users on a corporate network to notify them about updates, problems, or whatever the case may be. It has been a known fact that Windows Messenger could be used to send a message over the Internet, not just a private network. Until D Squared, nobody has been "intrusive" enough to use such an "exploit" for their own business gain. Read more..