Siri

You have to be connected to the internet for Siri to work.

You need a data connection, yes. Much of the voice recognition features of siri are too demanding for your iPad to handle entirely on its own (and the technology leverages several large databases for syntax recognition and such aspects of the processing of voice input) so the data is actually oflloaded to Apple's servers, processed, and what you hear back on the iPad is that processed data. So without a data connection, Siri simply cannot work.