Chris Melberger has 282,000 followers on Vine. Mitch Lewis' Youtube channel, The Kloons, has 220,000 subscribers. And Franchesca Ramsey's "Shit White Girls Say...to Black Girls" video has over 11 million views on Youtube.

With a six-second loop to a few minutes of video, a marketer could reach thousands of people with a message. The potential is huge. The problem is, three web stars said at an Internet Week panel Wednesday, marketers don't always get it.

Mr. Lewis said if a brand approaches him and his "Kloons" co-creators Greg Washburn and Nik Kazura, there has to be a frank discussion of expectations. Sometimes, he said, brands want to work with the sketch comedy trio, and then they say they don't like certain jokes after seeing a draft.

"Please trust us to know how to speak to the people we've been talking to for the past five years," Mr. Lewis said about communicating to his audience. He added that, from the start, potential sponsors have to be clear on their brand vision, how they want to be perceived and know exactly what that integration will look like with his comedy.

Vine sensation Chris Melberger, who masterfully nails the pithy video loop format and its tendency toward the absurd, said brands always stress that they want likes, views and followers. He acknowledged, however, that Vine is a new world. Not everything performs well, and Mr. Melberger said some contracts allow you to delete a specific post after 30 days. If one of his sponsored loops doesn't do well, he gets rid of it.

Franchesca Ramsey, YouTuber and writer for Upworthy, said social media users are unclear about sponsorships, and the audience can sense something is up. She cited an example in which several people used the same call to action about the same product.

"For content creators, it's really important to be honest," Ms. Ramsey said. "Your audience will appreciate if you're stingy with the brands you work with."

Finally, Ms. Ramsey said she appreciates when brands know her brand before contacting her.

"I get pitched things that are totally against my natural brand," she said, adding that she is contacted about weaves, wigs and hair-growing pills though she has natural hair. "Personalize your message, and do your homework."