The FTC “Guides Concerning the Use of Endorsements and Testimonials in Advertising,” officially go into effect tomorrow.

That being said, the changes have not slowed down so called “word of mouth” programs, especially by retailers in full holiday sales mode. “Don’t expect the FTC’s new guidelines on product endorsements to put a damper on social-media efforts,” wrote Advertising Age‘s Michael Bush today, citing numerous agency and internal brand marketers.

For example, blogger Melanie Notkin — known as Savvy Auntie — posted numerous Twitter updates from her sponsor JC Penny over the weekend and into today. Not all contained disclosure. Notkin herself admits to the rules being vague. “I don’t know. I try my best to make it clear,” she tweeted, in regards to if she only has to disclose her sponsor once, then is free to tweet and blog away with no disclosure.

Richard Cleland, Assistant Director of the FTC’s Division of Advertising Practices, told our sibling blog AgencySpy last Wednesday, in reference to tweets from tennis star Serena Williams: “When it is clear from the context of a communication that the celebrity is being paid, an additional disclosure is not required.” At this point, it seems the only thing that is clear is that everything is unclear. Marketers and bloggers alike should err on the side of caution, and it could be that “some will get screwed and some won’t” as one source put it to us this morning.