Nobody really knows! In part...

• ...it is because we can’t even agree on definitions, and
  
• ...it is because innovation is moving so fast.
  

But Simple Spark, an online catalog of web applications, recently provided one data point.

Their list of every browser-based application they can find recently crossed the 5,000 mark - and they celebrated by combining all 5,000 of those logos into a single five-minute-plus video.

Here it is: