Question: What is Xbox Live Silver?

Answer: Xbox Live Silver is a free version of the Xbox Live service. The main difference between the Gold and Silver levels of service is that you can't play online multiplayer games with Xbox Live Silver. You can still download content from the Xbox Live Marketplace, download games in the Xbox Live Arcade, and keep a friends list so you can chat and share your gamer profile and achievements.

So do you find acceptable that Micro$oft still makes you pay for something which you already paid for, in order for you to play the game online? The fact is with other consoles you don't have to, and they don't block you from access public servers.