Did you know that iTunes adds approximately 500,000 new accounts every day?
During his keynote address at Apple's WWDC, CEO Tim Cook said that iTunes now has a total of 575 million iTunes account holders, most of whom have a credit card connected to their account.
With that speed of growth, Apple can predict to crack the one billion mark by 2015 - at least. For comparison, Amazon.com has 200 million accounts, PayPal has 123 million, and Netflix, the world's most popular streaming website, has a mere 29 million active users.
Facebook and Google have more active users, but neither can showcase the unified storefront that Apple can, and neither have most of their users connected financially, which makes a huge difference in the eyes of many analysts.
Check out this chart, it's a great way to visualize how far ahead Apple is over other, similar competitors (and how many people are on Facebook now - with all the seniors jumping on board, it's starting to remind me of a retirement home).