Remember every xbox gets 2 or 3 free accounts with xbox live gold for 1 month. So if you don't want to shell out the dollars but want to play online for a certain game that's a good option!
I'm really glad they do this, since it's pretty important to try out any service for free before you buy. I'm happy to see that they are continuing to do this trial to give people a chance to experience Live.
There is a much better way to do this. Bing Rewards. I am a gold member and get a free month of Xbox Live every 22 days. It works and as long as Microsoft doesn't change the rules or requirements there is a good chance I will never pay for Live Gold again, and it is an official Microsoft mechanism so there is nothing that will get you console banned or anything like that.
What a great idea and how cool is it that someone can check the whole thing out without a dime being spent. Definitely something my friends and I are going to be doing.