Hosting entirely software based servers is one thing, but being able to maintain two different internet connections at once is different. Many computers do not support being connected simultaneously to wifi and LAN. You would need some hardware normally found in routers to support this.
Nah, there are ways - you're not connecting to WiFi and Ethernet (not LAN) at the same time, you're connecting via WiFi and sharing data through your Ethernet. Now, whether or not Ubuntu has a method for doing this, I'm not sure, but I know it isn't impossible. I've actually transferred files from one computer to another over Ethernet, and it was beautifully fast. ;)