While Facebook fared slightly better this year--up 3 percent to 66 on the ACSI's 0-to-100 scale--its poor showing suggests that consumers are open to trying a new social net. And, let's see, which might lure them away?

"The survey was conducted last month, before the widespread introduction of Facebook's biggest competitor, Google+, but Facebook's low score indicates that Google+ could easily pounce and gain market share if they can provide a superior customer experience," said Larry Freed, president and CEO of ForeSee Results, in a statement.

It's too early, of course, to predict whether mainstream social network users are willing to ditch Facebook for Google+. After all, griping is one thing, but packing up and moving to another social net is a major undertaking, particularly if it involves persuading friends and family to come along.

Then again, Google may be in a good position to pull it off. As Freed points out, Google is one of the highest-rated companies the in ACSI survey, while Facebook is in the cellar.

In the search engine and portals category, Google leads the pack with an 83, up 4 percent from a year ago. Bing is nipping at Google's heels with 82, a 7-percent improvement. ACSI scores over 80 are considered excellent.