conficker may in fact be alone in the world as recently the fbi busted a botnet kingpin and the virus code writer for the large mariposa botnet. with these busts all that remains in the "known list" of major viral botnets is conficker which is said to of had its hands on roughly 6million pc's worldwide.
trend micro and anandtech have more:
http://www.dailytech.com/article.aspx?newsid=19188