People are becoming more aware of the data being collected about them online. And that's eroding the trust they have with collecting companies, such as Facebook, Twitter and Google.

Asked which companies are the greatest threat to the future of privacy, 59% of 1,100 respondents cited Facebook and 40% said Twitter, according to a survey conducted by McCann. Thirty-two percent pointed to Google, almost doubling from the 18% who said as much when McCann conducted the same survey in 2011.

"It's not necessary that people feel Google or Facebook has done anything bad with data to date. It's what might happen in the future. It's a nebulous fear," said Laura Simpson, global director of McCann Truth Central, during a session on privacy held by Ad Age and IPG in Las Vegas on Wednesday.

By comparison, Amazon topped the list of companies consumers trust with their data, with 73% of respondents citing the e-commerce giant. It's worth noting that a majority of respondents also named Google to this category, but that number fell from 63% in 2011 to 53% in 2013.

Federal Trade Commission commissioner Julie Brill sat on a panel following the survey presentation and offered her thoughts on the findings. "I think consumers understand the first-party relationship with Amazon and understand Amazon is doing a lot of analysis of that first-party information," she said.

However the bigger issue is not with the consumer-facing companies collecting data but with those data brokers, ad networks and behavioral advertising companies most people have never heard of, said Ms. Brill.

"I do think we need legislation around privacy. … We actually need specific data-broker legislation," Ms. Brill said. She later reiterated her support for a Do Not Track system that would let people by default prevent companies from dropping tracking cookies on their web browsers that can collect data on their browsing behavior in order to target ads.

Ms. Brill also made the case for more consumer-friendly privacy notices and said advertisers should take a more active role in creating them.

"The ad industry is great at informing consumers of the things you want them to know about…I've often said if you all will kick the lawyers out of the room and you write the privacy notices and figure out how to give consumers immersive, short information on what will happen with their data," Ms. Brill said.

Following the panel, Ms. Brill discussed what topics are top of mind for the FTC at the start of the new year, including what she has her eye on during CES.