They are as popular as the Sit&Go tournaments. The thing they temptate the players are big and sometimes very big stakes. There are usually a couple of hundreds or thousands of people playing which automaticly raises the money you can win. The 'freezout' tournamnts are the ones where if you lost all your tokens you are out of the game and you have no chance to improve. 

You need lots of time to play in this tournaments because of the amount of people playing in it. The Sit&Go tournament lasts about 60-90 minutes and the freezout a couple of hours, and if we want to win in a really big online tournament we need dozens of hours to find out who the winner is.

This is what I like the most – big freezout poker tournaments! Apart from that the tournaments give you the opportunity to check your skills together with a couple of hundreds of players. They give you a chance to win a great money. Additional thing is that playing on the medium size tournament / the enry fee 30-50$/ you can meet up the best poker players on your table.