What could be a good opening sentence for this?
Why do you think people are so fascinated with celebrities? State your opinion and support it with reasons and evidence
Why do YOU think that people are fascinated by celebrities?
Check this site for some ideas.
http://en.wikipedia.org/wiki/Celebrity
you could write something about the paparazzi being all over them
and all of the glamour that surrounds their lives.
....or you could just say that people don't have lives of their own and decide to feed of celebrities.