Lots of people have been watching the World Cup. Many of them are also tweeting about it.
Twitter says it has counted more than 300 million tweets about the tournament during its first 15 days. By way of comparison, it counted 160 million tweets during the 16 days of the London Olympics in 2012.
It would be great to know how many people are tweeting about the World Cup, but Twitter isn't releasing that info. But via its public filings, we can at least map the change in Twitter's user base between the two events: In the summer of 2012, Twitter had more than 150 million users; at the end of March 2014, it had around 255 million.