There have been plenty of people whom have been willing to put their lives on the line in struggles where freedom of expression has been a central issue, and many who have died as a result. Tiananman Square is just one example out of many.

But I agree that most times it gets thrown out the quote is just empty rhetoric. Rather like "Give me liberty or give me death".

Incidentally the quote isn't by Voltaire. It appears to have been made up 100 years ago this year by a writer called Evelyn Beatrice Hall, as a summary of how she saw his thinking.