Many apps on FB are written with Java. The uploader is Java.
So there are three, but there are hundreds of thousands of websites that use JavaFX and JApplets on the web. Any website that has advanced tools that can not be displayed with AJAX due to complexity and or real time data display are usually written in Java
as Applets rather than Flash which is the popular choice for games, and adverts.
"LOL, if you have a Java application you need to re-write your entire application for iPhone or Windows Phone too. For Andriod, you can use mono to reuse your .NET libraries in a mobile application."
Windows Mobile is not too popular these days. How are you going to write a mono app for Android as an APK? Mono Droid is still alpha. Do you think an enterprise would actually release a commerical app with their name on it to the Android platform with Monodroid?
"real database in addition to Table Storage"
You can use SQLite in addition to Datastore and Datanucleus. App Engine is just one way you can distribute Java Applications in the cloud. There are actually hundreds of SQL implementations as well with Oracle, PostGRES, and MySQL.
Hey, my thread attracted a Java advocate. Welcome to Channel 9!