Just had the same issue with the driver's door handle, the car is 2008 reg 1.3 Multijet with 72'000km on the clock, so the warranty period is long gone.
Here in Finland the dealer wants a whopping 250€ to replace the handle (130€ for the handle and 120€ for labor), which makes it easy to look for alternative options. Thanks to MarcoVenturi's nice guide

and ebay I will fix it myself.
What bothers me the most, however, is that the handle looks to be exactly the same handle Fiat already used in Alfa 147. Even though Alfa 147 has suffered from the exact same issue for years even before Fiat 500 (Alfa 147 was manufactured from 2001 to 2010), the dealer (and factory?) has tried to claim that this is not a "known issue". What a load of crap.
Furthermore as the factory must have been aware of the issue, I find it staggeringly disgusting and unbelievable that they have not improved the original part in all these years (they have had 13 years to do so), but the hinge in the handle is apparently still manufactured of the rubbish quality alloy. I can only surmise that this is deliberate and just manufacturer's and dealer's cunning way of making some extra money.
Other than that and a few other very small niggles the wife and I are very happy with the car. Shame about the dealers, though.