From the NY Times:
By the time the arena in Brooklyn, which will be called Barclays Center, is built, there will be a total of nearly 100,000 seats to fill, 365 days a year.
For most of the last 30 years, there were only three arenas in the New York area: the Garden, Nassau Coliseum and the Izod Center, which opened in 1981 as the Brendan Byrne Arena. Each facility, at one time or another, was home to at least two major sports franchises. But in New York, as in the rest of the country, teams have sought and obtained new buildings — a trend that has contributed to a glut of arenas.
All of this competition can eat deeply into revenues.
The competition in the New York area is not just for fans and performers, but also for public subsidies, corporate sponsors and well-heeled tenants for luxury suites.
Interesting. This very problem was the reason an arena at Atlantic Terminal was eliminated from consideration by the state back in 1985:
So what changed in all that time? Why does the city need an arena there now when we have even more of them now than we had 24 years ago?