I agree; I have never had a problem using a promotion that you are allowed to type in and reserve through the website. These are usually "marketing discounts" as opposed to "comp discounts". I received an email from Wynn with the exact code you are asking about, and I have never stayed or played at the Wynn...I simply added my name to their "let me know what cheap stuff is happening" list.

I also agree with Yankeeflyer that when an offer says to "call in and mention..." that sets off an alarm bell that it's most likely a player promotion instead of a marketing one. Finally, a totally un-scientific metric is also the length of the code. Most marketing codes are "WDYNFALL" or something, whereas the discounts I get directly addressed to me because of my gambling and previous stays at the Flamingo are usually longer, along the lines of "1vwe342dfklq11w"