theodp writes "According to the FTC, 'celebrities have a duty to disclose their relationships with advertisers when making endorsements outside the context of traditional ads, such as on talk shows or in social media.' So, would the ringing endorsement of Zeppelin tour operator Airship Ventures that Sergey Brin gave to his 200,000+ Google+ followers last week fall into that category? 'Since getting to know the folks over at airshipventures.com,' posted Brin, 'I have had the pleasure of flying with them several times and this loop in the south bay is arguably the most scenic. I will probably give it another go when they get back to SF in October.' Forbes calls Brin 'an investor in Airship Ventures,' and others have speculated about a possible Google connection."