NAR rarely does anything about them, until someone (usually a competitor) turns you in. When you site starts moving up in the organic rankings your competition will usually turn you in!

NAR doesn't look for this kind of violation, but will act if notified.
Usually a letter from NAR's legal dept. will force an agent to change it. Sometimes it takes more, like involvement by the local board.
Unfortunately, NAR has no power to enforce against non-members, except through court action. So non-members (usually lead sellers) use it as they want.