The "Crackdown 2" game demo is enormous. You're basically getting a third of the game, with all the functionality, for free. Of course, that deals a little too good to be true, so Microsoft and Ruffian Games slapped a 30 minute time limit on the demo, so as to better encourage folks to pick up the full game. Unfortunately for them there's a very easy way to remove the time limit and play for as long as you'd like. Here's how to do that.
Step 1: Sign into Xbox Live and boot up the demo.
Step 2: When you get to the main menu, select "Demo Game," then "Play," then select your difficulty level and which character you want to be.
Step 3: Select your color, but don't hit A when the confirm prompt pops up. Instead, stand next to your console and unplug your network cable (or USB wireless router) while hitting A at the same time.
Step 4: An error message should pop up if you did this correctly. At the error message, hit cancel.
Step 5: Sign back in to Xbox Live and start the demo as normal. When the demo loads up, the timer should be frozen at 30:00 and won't tick down, thereby letting you play for as long as you'd like.
NOTE: For some reason, starting any kind of race (Rooftop or Driving) will cause this glitch to end, so make sure you don't do either.
Friends can freely join your game and they'll also have unlimited time. You can even earn all 10 of the demos achievements, but make sure you use the options screen to quit the demo properly or they won't count.
So there you have it. I played the demo for about 2 hours last night and had a delightful time. If you enjoy yourself, make sure you pick up the full game when it drops in about a week. Free stuff is nice, but those Ruffian guys gotta eat! Plus, you get to experience the magic of adversarial multiplayer, achievements and flyable helicopters!