You’re in the market for a new computer or camera or pair of pants. Who do you trust? Facebook likes to trumpet the value of “trusted referrals”—endorsements from your friends – but the real buzz is still from the blogosphere.

A new study from Jupiter Research found that half of all those surveyed who identify as “blog readers” (that is, people who read more than one blog per month, a fifth of total survey respondents) say that blogs are important to them when it comes to making purchasing decisions.

That doesn’t necessarily mean they trust the blogs. Only 15 percent of blog readers, and five percent of those surveyed said that the blog actually helped them make a reliable purchase decision. Not so hot? But social network recommendations were even lower: only ten percent of blog readers, and four percent of all those surveyed.

Results of the survey are similar when it comes to advertising: a quarter of “blog readers” say they trust ads on blogs that they read compared to only 19 percent on social networks.

Perhaps the most interesting take away: only a fifth of the total respondents said they read a blog at least once a month. If that’s the case, blogs may be a whole lot less a part of Web surfing than we tend to think. Or maybe, as design differences between blogs and mainstream Web sites continue to blur, people don’t actually realize they’re reading a blog.