Looking at the online black market

SC Magazine has a whitepaper from MessageLabs titled The Online Shadow Economy - A Billion Dollar Market. It reports on the research of MessageLabs Senior Architect of Development Maksym Schipka into the online criminal underworld, particularly Russian websites and forums.

You can buy customer written malware for as little as $250. Support is available for an extra $25 a month to ensure your malware continues to evade detection. As others have also reported, malware writers test their products against anti-virus software before release to guarantee that existing signatures will not detect it. This is where MessageLabs as been so great. The combination of established antivirus scan engines and their own Skeptic engine, a heuristic scanner, prevents malicious email attachments from getting through.

Schipka’s research suggests that malware authors can produce new, unique malware every 45 seconds
in order to keep it undetected. Signature based protections are not going to stand up to that attack.

If you do go to that link to read the research paper, be aware that SCMag will force you to register (I didn't find a bugmenot account). Also they will email the password you input in clear text. SCMag, thanks for cleartexting my password. I almost forgot the password in the one second between registering and receiving the "welcome" email.