I'm a progressive liberal fwiw, not a libertarian.
From the Wikipedia entry on Guilds: As Ogilvie (2004) shows, the guilds negatively affected quality, skills, and innovation. Through what economists now call "rent-seeking" they imposed deadweight losses on the economy. Ogilvie says they generated no demonstrable positive externalities and notes that industry began to flourish only after the guilds faded away. Guilds persisted over the centuries because they redistributed resources to politically powerful merchants. On the other hand, Ogilvie agrees, guilds created "social capital" of shared norms, common information, mutual sanctions, and collective political action. This social capital benefited guild members, even as it hurt outsiders.
The heyday of guilds lasted from around 1200 to 1700...