The FTC has updated their guidelines and you can find the updated file here: FTC Staff Revises Online Advertising Disclosure Guidelines. From the page:
“The Federal Trade Commission today released new guidance for mobile and other online advertisers that explains how to make disclosures clear and conspicuous to avoid deception.”
Did you know that the FTC has a blog? Here is a post entitled FTC Reboots .com Disclosures: Four Key Points and One Possible Way to Bypass the Issue Altogether
Essentially they updated the guidelines to make is crystal clear that disclosures are needed no matter where the advertisement is. Here is an excellent article discussing how it applies to twitter entitled FTC Lays Down the Law on Endorsed Tweets.