Hi-tech criminals use botnets to send out spam . It was found in the US that "More than 2.2 million US PCs were found to be part of botnets, networks of hijacked home computers, in the first six months of 2010"
This short article has interesting figures on the number of people who participate in video calls. It also conclude that " The research firm said that widespread video-calling adoption in the mobile space could be "held back by a lack of interoperability between different devices."