Why do people already think the Trade for Iverson is a fail for Detroit?

The Pistons were obviously not getting anywhere with Billups. Their last championship was with Billlups back in 2004 but they have not made it back to the NBA Finals with Billups since 2005. I think a change needed to be made since the team is still under the Celtics and would not contend this year with Billups. What are your thoughts?