I didn't use the phrase "ethical restrictions," and I'd suggest that practical considerations are as important at Google as they are at Webmaster World. That's one legitimate reason, though not the only legitimate reason, for having ad standards. Consider: Banning certain types of alcohol advertising from AdWords is a practical thing to do if there's a risk that software filters might not catch ads for mail-order liquor sales or liquor ads with prices (both of which are illegal in some jurisdictions). It may also be a practical thing to do if Google is concerned about possible PR fallout. Or it may be a practical thing to do if you're the person in charge of AdWords standards and Sergey Brin or Larry Page tells you, "I really hate it when teetotalers from MADD spray-paint protest slogans on our Boeing 767."
[edited by: tedster at 10:39 am (utc) on Dec. 10, 2008]