Most of us still don't like giving out our credit card information on social networking sites, according to a poll of 2,630 adults by Harris Interactive for Digitas.

And that could mean trouble - at least for now - for Facebook and other social networks hoping to make good on predictions that social media commerce will reach $30 billion within five years. The poll, which included 2,247 people who identified themselves as social media users, found attitudes that mirrored those confronting retail brands when they opened online stores a decade or more ago.

Men between the ages of 18 and 54 who make $35,000 or more per year are the most likely to make purchases through a social network, but overall, 55% of poll respondents said they were still reluctant to turn over credit card info. The potential, however, is there: 75% of respondents said they were more likely to purchase a product or service if it was endorsed by a friend on social media.

The survey results, presented in an infographic below, also explain how brands can improve social media sales conversion rates.