If I see a registration from a confirmed proxy server I ask the new member to explain why they are using a proxy server. If they don't reply I delete their membership.
If I see that the IP is coming from a proxy server like Japan, Israel, Korea, etc. It doesn't show a city just a dot on the country itself. I ban them immediately. They're up to no good. They usually are spammers and always use the birthday of Jan 1, 1980