Networking cards don't cost too much, but it's slightly better to run ethernet. As USB runs at 12Mbps and ethernet is 100Mbps (I think 100Mbps, gosh I should know this I'm taking networking classes to get my CCNA). You can go to the store and buy a really good one for about 10 bucks, but, unless you're running super fast internet, you probably don't need it. As you probably wont be going more than 12Mbps. Or are you?