"Sitting at my desk, the idea just dawned on me. Why not write this romantic story about how we met and leave it open-ended?" he said.
Allan said he knew that Karcher wanted a Kindle anyhow, so he waited until the couple's two year anniversary and presented her with his gift.
He walked her through the device and then said he'd already taken the liberty of downloading its first story.
"She read it out loud and as she reads it, she sort of pauses and says, 'What is it? What is this story?'" he said. "I'm getting super nervous at this point and pulled the ring out of my pocket."
When Karcher reached the end of the story, he proposed.
"It's just a fantastic little tool," Allan said about the Kindle. "It really made it a lot more memorable.
And when they get married this May, he said the Kindle might join them at the altar -- maybe even in the hands of their officiant.
When 26-year-old Matt Van Horn got down on one knee, the entire Internet could have been following along.
In proposing to his girlfriend Lauren Fishman, 26, last August, Van Horn enlisted the help of his friend (actually the same Chris Hutchins of the Path proposal) to use the Web application Qik to live-stream the entire thing.
Not only that, but he leaned on the location-based network Foursquare and Twitter, too.
"Obviously, I've been a big nerd my whole life and she's always known that," the San Franciscan quipped.
Van Horn told Fishman that he would be out of town for the weekend, but then had a friend lure her to their favorite spot in the city.
He hid behind a rock and waited. When he got the signal that she had arrived, he checked into the park on Foursquare, which posted the live-stream URL to Twitter.
The tweet not only alerted Fishman to his presence (she receives his tweets as text messages on her phone), but let friends, family and total strangers watch the whole proposal online.
"The thing that made me the most nervous was … she actually makes me stand on the one knee for 23 seconds without any indication of positive, negative, anything. Just like hand over face," said Van Horn, who runs business development for the social network Path. "So that was pretty terrifying. Twenty-three seconds when you're proposing, that's a lifetime. I was confident she was going to say yes but it was still nerve-wracking for the 23 seconds."
Ultimately, Fishman said yes and Van Horn said she appreciated the memorable marriage proposal.
But when it comes time for the wedding, the couple has decided it will be a low-tech affair.
"It's going to be the anti-social media wedding," he said. "Our wedding is going to be a smaller, more intimate setting and not one for sharing with everyone in the world."
For one Cincinnati couple, it was the deal of the day that led to a lifetime of love.
In January, 25-year-old Greg Hill conspired with Groupon to create a special deal just for his girlfriend Dana Burck, 24.
Titled "A Surprise for a Dana from a Greg," the one-day deal went live across the Cincinnati market but was available in a limited quantity -- for only one.
Under "The Fine Print," the deal said, "Groupon entitled to no less than 15% of your marital bliss. Either party may develop a snoring problem. One or both participants will not always look like a 20-year-old. Good luck, you kids."