Also, it is in the interest of the club to have a capacity lower than demand. If a club, any club have a massive ground so anyone can get in, sooner or later fans get complacent and can't be botherd going espically if ticket prices go up. A greater demand creates interest in getting hold of tickets. The way wages are going, the bubble could burst in England, and clubs could struggle to fill the stadia.
I remember an ex-colleague of mine (an Arsenal fan who lived for a short time in Spain) told me about a small team who got promoted to the top league and then built a brand new massive stadium, it was also used in the World Cup '82. They didn't get teh crowds to pay for it, so were forced to sell their top players, got relegated and are still a lower division team with a fantastic if empty stadium.
It is not difficult to imagine the same thing happening over here, especially if the bitters built their Kings Dock stadium - ho ho.