I really don't see this catching on in the US.
Here in Beijing lots of people (me included) ride electric bikes because it's too expensive to have a car and traffic jams are so bad it takes me 15 minutes to ride to the bank whereas it would take me about 1 hour to get there by car during rush hour traffic. Motorcycles aren't allowed in the center of the city so an electric bike is really convenient for getting around.
Then there's the question of money. I bought my bike for 2,100RMB (about $300USD). This is a little under half a month's salary for the average Beijinger so these things are very affordable especially compared to cars and motorcycles. I supect this is one of the reasons electric bikes are getting popular in places with a lot of poverty like India.
Then there's lifestyle. Here there's no Costco so I'm not hauling bags and bags of groceries at one time. Also I live in the neighborhood where I work so my commute is only about 10 minutes. That's the perfect range for one of these bikes. If you had an hour commute like many people in the US, you'd never be able to take the bike since the average charge seems to get me through about 45ish minutes before I really need to recharge. That's with peddling to help out the battery.