I think this website skews people's perception of tank size. Most people who come to my house think a 55g is a huge tank.
On the HGTV channel they were profiling this guy who had spent $100,000 on his basement remodel. He had a 20 gallon tank built in the wall right next to his lay-z-boy chair. It looked like an airplane window to me... But he (and the hosts of the show) thought it was great.