In 2012, Professor Daniel Lemire and I bet $100 over the question of whether tablets would replace PCs.
Specifically, the bet was, "In some quarter of 2015, the unit sales of tablets will be at least twice the unit sales of traditional PCs, in the USA." Loser donates $100 USD to the charity of the winner's choice.
It's 2016, and tablet sales went far higher than I ever expected, approaching PC sales, roughly 60M/year units for both tablets and PCs in the US. But tablet sales seem to have peaked, with Q4 2015 unit sales worldwide actually 14% lower than the previous year, which is worse than the 8% decline in PC sales.
There are other surprises. One of my concerns was that a very cheap tablet would dominate the market, and Amazon did come out with a $50 tablet that got relatively good reviews and nearly tripled Amazon's market share on tablets. There hasn't been enough time yet to see what happens with very cheap tablets, but tablets this cheap are a different category than the tablets that were around in 2012.
Another concern at the time was hybrid tablets, so tablets with detachable keyboards that function a lot like laptops, and whether they'd blur the line between PC and tablet. Hybrid tablets have done very well -- a major category in tablets -- and look likely to continue to grow over time.
The last concern at the time was whether tablets could thrive despite the pressure from increasingly larger and more powerful mobile phones. That seems to have been the biggest issue. Phablets are getting as large as early tablets, and tablets that try to be much bigger than a smartphone proved too unwieldy and sold poorly. After all, who needs a tablet when you've got a mobile that's almost as large?
The broader question in the bet was whether people would stop using PCs. PC sales have been in decline, though the pace of that decline has slowed recently. What seems to be happening is that people are continuing to use multiple devices, which was a visible trend back in 2012.
A phone is great when you want to do something quickly on the run. A bigger screen is good when you need to do a lot of reading. A keyboard, mouse, and large screen become useful when you're producing instead of consuming. If you need to do all of these, there's no reason to only have a phone, only a tablet, or only a PC. Instead, people often have all three and more.
Even though I technically won this bet, I want to congratulate Daniel Lemire on this getting much closer than I ever expected. I also admire the bravery he had to take the bet, especially with such favorable terms, and appreciate what I learned from this. The terms were that the loser donate $100 to the charity of the winner's choice, and I'd like to match the donation. Daniel and I will both be donating $100 to the Wikimedia Foundation, which runs Wikipedia.
Update: Daniel's post is up: "Lost my bet: the PC isn't dead... yet".