Among tablet computers, Apple’s iPad owns nearly 100 percent market share.

But The iPhone Blog, among others today, writes that JT Wang,  the chairman of computer maker Acer, thinks that this share will drop to 20 to 30 percent.

The chairman is talking about what I call dethroning the king.

When one product comes to define a category, filling that category up completely — physically, on shelves; and psychologically, in consumer minds — that product is the king of its domain.

The iPad is king of tablets.

The iPod is king of MP3 players.

Adobe’s Photoshop is king of professional photo editing.

Amazon is king of digital book readers.

Google is king of search.

TiVo was king of digital video recording.

Palm was once king of the smart phone. (Remember that? Feels like it was eons ago. Or part of a short dream you only remember bits and pieces of.)

Xerox was king of copies.

And Microsoft was once king of personal computing.

It’s difficult to displace a king. But it’s far from impossible, and it’s been done many times before.

Here’s what must happen for a category defining product to be displaced by others:

  1. Alternatives must cost much less, undercutting the king. TiVo lost its position as DVR king because cable companies like Comcast made it free and simple to get an alternative. TiVo still costs $300 to $500 dollars, depending on the model. Cable DVRs are still free upfront. This is why TiVo will never be king again. Critically, the price difference needs to be dramatic. For example, a $400 tablet has no chance of overcoming the iPad. But a $99 tablet might.
  2. Alternatives must be plentiful, overwhelming the king with volume and consumers with options. Palm was displaced as king of smart phones by a number of alternatives from many different makers: RIM Blackberries, Nokias, etc. Although the iPhone never became the smart phone king in the purest sense of the phrase, was caught and surpassed by Android devices through sheer volume. There are countless Android phones, from every major wireless carrier in America. There’s only a couple of iPhones being sold, through a single wireless carrier. For now. (It’s no accident that a Verizon iPhone is coming soon. Now chasing kings in the smart phone business, Apple needs to create as many iPhone options as possible for people.)
  3. Alternatives must make people feel like they are missing something by not having them. Blackberry users feel tempted by alternatives all the time for this reason. iPod users do not. Which is why no other manufacturer has been able to overtake the iPod as king of the MP3 category. Nobody has been able to make a better one. Same for Amazon’s Kindle. And same for Google (in search, anyway).

If you want to overtake the king — and become king yourself — you must be much more affordable and/or present users with many alternative options and/or create amazing products that make people yearn for you.

Difficult. But not impossible.