AppData, meanwhile, says the number of Pinterest users connected to Facebook in the past 30 days declined to 8.3 million from 12.2 million.
"The numbers show slowing user growth, (the) negative impact of redesign and declining buzz level on Google Trends," IDC analyst Karsten Weide says.
What impact, if any, those figures have on the hype surrounding Pinterest is anyone's guess. The 2-year-old start-up has an estimated value of as much as $1 billion and is a hot acquisition candidate, following Facebook's $1 billion purchase of Instagram.
The dip could be interpreted as a hiccup in the app's inexorable path to Internet riches, says ComScore analyst Andrew Lipsman.
Pinterest did not comment directly on the reports but said in a blog post Wednesday that it had its "highest traffic days ever" on Monday and Tuesday. It did not provide figures, though market researcher Experian claims the site is the third-most-popular social network in the U.S., behind Facebook and Twitter.
For historical context, Lipsman compares Pinterest's hockey-stick-like growth to Twitter's ascent a few years earlier. "After periods of major growth spurts, it's natural for things to subside," he says.
What the figures tell is that despite formidable numbers, Pinterest has a soft user core that has yet to solidify — just as Twitter did in 2009, Lipsman says. Now, Twitter users are among the most fervent among social-media companies.
For now, some consumers are re-evaluating Pinterest. "I need more time and motivation — not more ideas and recipes," says freelance writer Cathie Ericson.