And on a shared hosting account you can host unlimited domains. I won't name them, but on company with the word "host" in it's name spelled out in the T & C that each account is limited to 30,000 individual files. If each site only had one page/file how could I host an unlimited number of domains?
You still need a file to generate them. Unless you could get all the domains to point to the same documentroot or use a symlink or something.
Anyway, hosting companies like that massively oversell their capacity knowing that most people won't use it. If you actually tried to put up 30,000 (or, heck, even 300) active domains, the server would probably just die under the load.
Anyone have the number for the FTC?