The media mogul and former talk-show queen has been gushing for weeks about Microsoft's new Surface tablet, which she compared to a Mercedes and named one of her "Favorite Things" of 2012.
On Sunday, she went a step further, sending a Twitter message to her 14.8 million followers saying "love that SURFACE!" and adding that she'd already bought 12 of the devices for Christmas gifts.
There's only one problem. Winfrey -- or whoever manages her Twitter account -- sent the tweet from an iPad.
The people of the Internet, who never miss the opportunity to poke fun at an online gaffe, took notice.
"She does have legions of fans, making her an effective marketing channel for Microsoft. Except for when the narrative around her promotion is tossed on its head by a foolish, and utterly avoidable mistake," wrote Alex Wilhelm on tech-news site The Next Web.
"Surface ads, now brought to you by iPad."
Tweeted All Things D's Kara Swisher: "Ok, this made me laugh out loud."
But other observers said people shouldn't read too much into Winfrey's tweet.
"The tweet being sent from an iPad doesn't necessarily mean Oprah prefers the iPad over the Surface RT; just because you bought a Wii U doesn't mean you'll never use a Sony or Microsoft console ever again," wrote James Plafke at Geek.com.
Besides, some bloggers have noted that no official Twitter app exists yet for Windows 8, the new operating system on the Surface, although Twitter says it's building one.
So maybe there's room in Oprah's heart for two tablets? Apple fans may remember the original iPad made Oprah's "Ultimate Favorite Things" list back in 2010. "Words cannot describe what I feel for this magnificent device," she said at the time. "I really think it's the best invention of the century so far."
At least, until the Surface came along.