In the switcher, it seems that people are putting paths (e.g. domain.com/blog) where they should be putting domains (e.g. domain.com) - and this causes invalid paths on the site.

A warning to look out for anything incorrectly containing a /

Also put some text to point out that the plugin does not magically create the DNS entries for arbitrary domains. Just becuase you typed in m.domain.com does not mean it is going to resolve.

(In a future version, there could even be a little socket lookup sanity check to see whether the domains resolve)