The short answer is that the commercial is bad, really bad, horrendous. If you have not seen the commercial, I have posted a YouTube video of the commercial below.
You have to wonder what Fiat's marketing objective was with this commercial. What were they trying to tell the viewer? Honestly, I'm not really sure and that's the first thing that is wrong with the commercial. My best guess is that they want to show that their little car is zippy, fun to drive, and attractive. The problem is everything else happening in the commercial really distracts the viewer from that core message. I'm left wondering why everyone is chasing the car and why a motorcycle is jumping over a bus. Is it because they love JLO or because they love the car?
Secondly, does Fiat really expect us to believe that Jennifer Lopez drives one of their cars? We can easily believe that Justin Bieber uses Proactiv or that Joan Rivers wears her line of jewelry. Those endorsements are believable. Maybe we could believe that JLO rides around in an Escalade, BMW or Jaguar, but not a Fiat.
The worst thing about the commercial comes at the end when she all the sudden busts out some horrible dance move. From a marketing perspective, how does this help convey Fiat's message (whatever that message is)?
Fiat should leave the celebrity endorsement commercials to Chrysler who did an awesome job with their Eminiem ad (see below):