Microsoft added detection and removal for "Zbot" to its MSRT tool one of the most widely known active botnets. Although the malware itself is quite complex and varied, the technical acumen required to use and distribute it's actually quite low. Toolkits to create the malware are easily attainable and quite simple to use as following screenshot shows.
Underground forums are teeming with questions ranging from very basics about configuring malware to people boasting about the size of their botnets. Even botnet controllers are themselves quite varied, from apparent hobbyists to those that likely have more nefarious intent.
This family is quite prolific even if the intent behind some of the botnets is unclear.