Most small businesses I have worked with use peer-to-peer networking. Before I arrived on the scene, most of the machines were running at administrator level, did not have passwords (or if they did, at least one machine's password, if not all of them, was "password," the network name was usually "workgroup," and they had no idea what a firewall was. If they had a hardware router, the router administrator name was "admin" and the password was also "admin."
The usual reason I was called in was because the computers were running slower than molasses in January, often took a half hour to finish booting and then were almost unusable, and the browser home page was something you would not want your children to see...
Same here.
The fun part is when they start expanding and you hand them a quote for Windows Server to control their now larger netowrk... ugh...