You wrote in one of your great NginX articles that sometimes there is no need to use multisite but instead to use multiple individual wordpress installs.
If have 40 domains, one owner/webmaster. Each domain is unrelated to another (one travel affiliate site, another adsense, third news, fourth review etc..) Each site would have a separate theme and a separate set of plugins independent of others with few overlaps. None of the sites would give users the ability to register and create their own subdomains.
Would you think it be better to run the 40 domains as a single subdomain multi-site, or have the 40 individual wordpress installs?