Here is a bit of trivia that you might find interesting(taken from Wikipedia):

In 2005, the sculpture attracted some controversy when a professional photographer without a paid permit was denied access to the piece.[55] As is the case for all works of art currently covered by United States copyright law, the artist holds the copyright for the sculpture. This allows the public to freely photograph Cloud Gate, but permission from Kapoor or the City of Chicago (which has licensed the art) is required for any commercial reproductions of the photographs. The city first set a policy of collecting permit fees for photographs. These permits were initially set at $350 per day for professional still photographers, $1,200 per day for professional videographers and $50 per hour for wedding photographers. The policy has been changed so permits are only required for large-scale film, video and photography requiring ten-man crews and equipment.[56]