Marketers in some niches (mainly gambling, but I've seen some pharma) will sometimes choose to promote naked IP addresses instead of domains. This is because while it's easy for countries to ban access to certain domains, they usually don't treat IPs the same way. So if a casino site uses puts their site on 234.123.456.888 for example, spams enough backlinks to the IP that it starts ranking and getting traffic, any countries that routinely ban gambling related domains will usually let it slide, and the site can continue to receive lucrative traffic from these countries.
You can do the same by setting up a VPS with a web server like Apache running, and upload your site to the web root directory. I don't think there's currently a 3rd party market for high metric IPs though.