Below is an example of what a typical entry in this database will look like:
So why is Google investing in this project, besides out of the goodness of their hearts?
First of all, don't get me wrong. Google is a charitable place. They give a ton of money to non-for-profits, science fairs, technology competitions, green energy, third-world development projects, and other great causes. More money than most of their competitors. But sometimes their charitable investments can also have a strategic value for the company.
In this case, this move can help them compete with Apple.
... wait. What?
Yes, Apple. Specifically, the competitive threat posed by Siri. Many have speculated that over time, Apple's Siri can turn into a fully functional search engine. In this case, Apple wouldn't need Google to power its search anymore.
The biggest thing Siri has going for it is being able to provide factual answers. It does this by relying on data from Wolfram Alpha, which has its own database of structured information. The simplicity of both Siri and Wolfram Alpha is that you can get a direct answer rather than a link.
Google has been giving more and more direct answers to search queries on Google.com. Most of these are already powered by Wikipedia. If Wikidata succeeds at creating its database of facts, Google's ability to provide direct answers will greatly improve.