that you cannot/must not select the WHOIS opt-out option if you are trading in any way via your domain name, or if you have purchased the domain name with the intention of using it for any commercial purpose.
Only non-trading individuals are able to opt-out of having their address details shown on the WHOIS. Non-trading individuals are defined as registrants who are not businesses and who are not using or intending to use their domain name in the course of a business, trade or profession.
You're supposed to declare it at point of domain registration and you can get into some legal hot water if you use a domestic address for profit trading.
Think about it. You register a domain. It is registered to you, under your name, at your address, telephone number and so on. It stays with you for normally two years or more. How difficult would it be in any typical two year period to check the domain, considering you register it with all of those credentials from the outset ?
that you are a 'consumer' - i.e. someone who has registered the name for a non-commercial use. If however you opt out of the full public WHOIS register and you use a domain name that falls within one of the Nominet UK registration classes for commercial purposes you are contravening the terms and conditions of your registration contract. Nominet monitors registered domain names and if they detect a commercial use of the name they will simply opt you back into the public register without your knowledge or consent. If they feel that you are flagrantly breaching the contract rules they may even remove your domain name regostration fom you completely, and your web site will vanish from the internet.